The Journal of San Diego History
Fall 1975, Volume 21, Number 4
James E. Moss, Editor
Thomas L. Scharf, Assistant Editor

Images from the Article

The route followed by the Serra expeditions (plural) from Loreto to San Diego has been the subject of much study, much field work, and much argument. As of now, many parts have been determined beyond reasonable doubt, much competent field work has been done on others, and only a few are disputable.

Recent studies have disclosed many sectors of the trail from Loreto to San Diego. This, although following in part the Jesuit, Franciscan, Dominican and military trails that ran the length of Baja California, is hardly the Serra Trail. After Serra’s initial journey, the support of the California Missions required perhaps ten million mule-miles of travel, which surely obliterated the original path, replacing it with the wider, more deeply worn, and usually straighter trail, which survives to this day.

Even among professional historians, the magnitude of the Serra and related journeys is seldom realized. Fig. 1 shows its length graphically. The first part, from Loreto to San Diego, equals a trip from San Diego to Socorro, New Mexico; or from New York City to Lansing, Michigan. The journey of the military party, which led to the discovery of San Francisco Bay, equalled a trip from San Francisco east to Hoyt, Colorado; or from New York City to Fort Dodge, Iowa.

The length of peninsular California approximates the distance from Washington, D. C. to Des Moines, Iowa; or slightly exceeds that from Mobile, Alabama to Chicago, Illinois. When climate and terrain are considered, the magnitude and difficulty of Serra’s journey is comparable to one over the old slave trail from Timbuktu to Tamanrasset; or along the caravan route between Nebit Dag and Samarkand.

Chief travel problem in Baja California, at most places, in most seasons, is “falta de agua.” By all rational climatic classifications, most of the area is desert, as is indicated by Fig. 2. Climatic charts for selected stations comprise Fig. 3. Note the fall precipitation maximum in the south, corresponding roughly to the hurricane, or “Corondazo” season.

Rainfall profiles, and rainfall distribution by seasons, are shown in Fig. 4, which is based on best available data, but should be regarded as only approximately correct. Standard meteorological measurements do not take into account the effects of fog, which are important at Candelaria, the northern part of the Sierra San Borja, and on the Llano del Berrendo. The actual and smoothed crest profiles of peninsular California, in the center of this figure, give a rough idea of some of the terrain problems.

Aridity of the Sonoran Desert Region, as computed by De Martonne’s index, is shown in Fig. 5, also based on best available data. With this index, the aridity is greatest when the numerical value is least. In some parts of the central desert of Baja California, the aridity index probably approaches 1.5, but firm evidence for this is still lacking.

These charts and tables give a reasonably good objective idea of the aridity of the peninsula. For a subjective impression-what you will feel in a broken-down Jeep when your canteen is empty—I refer you to the writings of Dante Alighieri.

As a natural consequence of the weather and climate, mirages and shimmer inhibit surface observations, rough air makes flying unpleasant, and dust lowers the dependability of machinery and the accuracy of instruments. Dust static, discharges from ordinary thunderstorms and from the “tormentos secos” common over the backbone of the peninsula, interfere with radio communication.

Recent paleoclimatic studies suggest that much of Baja California has undergone considerable desiccation since 1750; and there is clear evidence of a cycle of arroyo cutting in the higher areas, and deposition on the flatlands, starting about 1870, and ending about 1930, much like that evidenced in Sonora.

From these climatic indications, we can see why Father Baegert declared that “California is the worst place on earth.”

The terrain of Baja California includes everything from flat desert plains to nearly impassable mountain ridges. Generalized cross-section of the peninsula, representative of the northern part, and of the area west of Loreto, comprises Fig. 6. In the central part, due to multiple faulting the ridges are more nearly like the basin and range country of southwestern Arizona, and numerous fossili-ferous sediments, probably marine cretaceous deposits, first clearly described by Ferdinand Consag in 1751, are exposed.

In much of Baja California, the Gulf coast is a rather narrow bajada, terminating westward in the steep escarpments of the peninsular ranges. Boundary here is usually related to a fault scarp, and here we commonly find hot springs, such as those described by Melchior Diaz in 1540, Father Kino in 1684, and Father Linck in 1766.

Some of these hot springs are still active, and furnish unique locations of value in historical studies.

The main peninsular ranges, although somewhat similar in structure, are not a single geologic entity, having differing core materials. The “backbone” of the peninsula is interrupted, north of San Borja and south of Rodriguez, by tear faults, which, aided by erosion, have produced topographic lows.

Westward from the summits, for some miles, extends an eroded lava plateau, deeply trenched, in many places, by ephemeral streams. This plateau consists of alternate layers of hard rock, usually basalt; and softer materials, such as tuff, breccia, and the erosion products of stratigraphically older formations. Because of this layer-cake stratigraphy, exposed faces of the plateau have a stair-step structure, with the nearly vertical risers composed of hard lava; whereas the gently-sloping treads are floored with tuff and breccia. The softer beds form porosity reservoirs, so that springs and seeps are found atop the basalt strata; and tinajas are found in plunge pools eroded into the harder rocks by ephemeral stream flows. The exposed faces of the plateau are here called the intermediate slopes.

West of the plateaus are bajadas, which grade into, or are interfingered with, marine deposits. Presently available evidence, chiefly abandoned shorelines, suggests that parts of the western bajadas were submerged in the recent geological past, so that many isolated mountains, such as the Sierra de Santa Clara, were once offshore islands, separated from the peninsular mainland by very shallow seas. This is particularly evident south and east of Vizcaino Bay.

Near Santa Rosalia, the general picture has been complicated by multiple faulting, and the resultant family of summits partly obscured by recent outpourings of lava from Tres Virgenes Volcano, whose eruption in 1744 was recorded by Father Consag.

Despite the thorough and competent work of Forrest Shreve and Ira Wiggins, a meaningful botanical map of Baja California cannot yet be drawn to a scale useful to our present study. In very general terms, the poorly watered bajadas and intermediate slopes support a thin cover of desert plants, such as cirio. In those few areas where water is relatively plentiful, palm trees and wild fig are found. On the upper intermediate slopes and parts of the plateaus, orographic rainfall and fog condensation encourage sparse growths of grass—most important for horse and mule travel—in some places. The higher summits, except in the Sierra San Pedro Martyr, tend to be relatively bare, although it is hard to find a square yard of Baja California, except for active sand dunes, recent lavas, or modern playa floors, that is completely devoid of plant life. Eliminated from this statement are such man-made environments as paved roads and parking lots.

In the Sierra San Pedro Martyr, which extends upward almost two miles, heavy rainfalls and occasional snowfalls support open forests of pine, oak, and aspen, interspersed with soggy alpine meadows. Drainage from this highland, largely to the west, permits some streams to flow for six or more months each year.

Since the 1700s, the botanical picture has been changed somewhat by the introduction of the date palm, the cultivated fig, grape vines, and a variety of food crops. The provenance of some of the Baja California plants, such as the wild fig, is still a matter for conjecture; and the ecological effects of the introduction of grazing animals, exotic plants, and various diseases, are still not fully evaluated.

In this not too salubrious environment, from about 1685 on, the Jesuits conducted extensive explorations, and founded a chain of missions, most of them successful, from San Jose del Cabo north to Santa Maria. At the time of the Jesuit expulsion, in 1767, the missions as far north as San Borja, despite poverty, water shortages, supply difficulties, and disease, were a going concern. Jesuit explorations had penetrated into lands farther north, at least to the head of the Valle de San Felipe on the east coast of the peninsula, and beyond San Fernando de Velicata near the west coast. Because of personnel competence and excellent recordkeeping, we have a rather complete account of Jesuit activities; and many of the exploration reports, such as those of Fathers Kino, Consag, and Linck, would be classed as competent work, even by twentieth century standards.

When, for reasons largely political, it was decided to occupy the lands of Alta California, a crash program of exploration and settlement became necessary. This, conducted under joint military and Franciscan auspices, led to the settlement of Alta California. This successful enterprise entailed the use of four more or less separate parties&$8212;two ships; and two land expeditions, the first headed by Captain Fernando Javier Rivera y Moncada; and the second, of which the best known member was Fray Junipero Serra, O.F.M. With the route and trail of the Serra party, and what eventually developed from it, in Spanish and Mexican times, we are chiefly concerned here.

Travel, in Baja California in 1769, was difficult, and was confined to walking, or riding horses or mules. No wheeled vehicle, at that time, had ever gone the length of the peninsula, and no four-wheeled vehicle, up to now, has followed the entire Serra trail. The Serra route, and the Serra trail, will be better understood if we consider for a moment the necessary requirements for mule travel. Although the mule is a tough and resilient animal, who can continue to walk for some time after there is no food, water, or rest, his sustained walking rate declines rapidly with underfeeding, dehydration or overworking. His recovery from a single difficult short journey is rapid; but repeated episodes of overstrain tend to produce lasting disability. In general terms, pack and saddle mules on a long journey must have water and food every 48 hours and rest about every 40 miles, or many of them will “burn out”, becoming marginally useful on the rest of the journey.

Search for the Serra and other trails in Baja California is not as simple as is sometimes believed, for the entire peninsula is crisscrossed with trails, some made by men afoot, others by pack and saddle animals, and still others by wheeled vehicles. If the original route was nearly optimum, the newer trails, including a few paved roads, have obliterated many parts of the older trails. This proliferation of trails, observable on the ground in many places, is even more apparent when the land is viewed from the air under suitable lighting conditions. Most of the older trails converge at water holes, and many “new” water holes, most of them seasonal, cathartic, or now dried up, have been located by following old foot trails.

Characteristics of man trails and mule trails are summarized in Fig. 7. The fracturing and subsequent erosion of the surface of the mule trail is almost surely due to iron-shod hooves. From the widths of the horse and mule trails in Baja California and Sonora, it is probable that the Spanish pack and saddle animals did not “singlefoot.” Appearance of a man trail over which no ridden or loaded animal has ever passed is shown in Fig. 8. This is an Areneno Papago trail at Pinacate, Sonora, an area for which we have a very complete and dependable travel record dating back to 1540.

Mule trails, in Baja California, went from mission to mission over optimum routes. Optimum here does not mean in a straight line, or over a path of least gradient, but usually entailed detours to reach intermediate water holes, and routings that took them through areas of maximum grazing. Much of the old Jesuit trail went over the plateaus, where temperatures were lower than on the coastal bajadas, where grass was more plentiful, and where air motion was greater than at sea level.

Mule trails, wherever found, tend to have some definite characteristics. These are outlined in Fig. 9, a group of generalized figures incorporating some observations by the late William H. Jackson, who had extensive experience as a packer about a century ago. Using suitably named fictitious points, where travel by a few animals was fairly rapid, and there were no geographical constraints, travel might have been in a reasonably straight line between the terminals, as in A.

When travel was slower, so that the animals grazed en route, and there were still no geographical constraints, the single trail is replaced by a multiplicity of trails, complexly braided, covering a lunate area between the points, as in B. Such braiding of trails can be seen from the air on the plateau between San Javier and Comondu, and in the plain northeast of San Telmo.

If, as is the usual situation, geographical constraints are present, the trail pattern will look something like C. Here, the animals do not usually climb steep hills to graze; and, Mission Santa Gertrudis.

This first section of the trail, having been used extensively by the Jesuits before the Serra journey; and having been worked on over a period of years by Indian neophytes, is relatively easy to find and follow in most places. Small sectors have been removed by erosion; sectors in arroyo bottoms have been obliterated by flood erosion; some parts are rather heavily brush-covered; and a few parts have been obliterated by modern vehicular travel, mostly since 1960.

The next sector, from south of Mission Santa Gertrudis to San Juan de Dios, is shown in Fig. 11. In the first part of this, we have three sets of trails extending from Santa Gertrudis to San Borja, and all show some signs of Jesuit workmanship.

The first of these (1 in Fig. 11) goes very roughly northward from Mission Santa Gertrudis, usually east of and above the modern wheel tracks, to about the head of Arroyo Santa Isabel. Here, west of the site of La Mina, the trail forks. One branch goes northeastward to the Puerto de San Francisquito (about 11 miles north of modern El Barrio; the other veers northwestward, up a broad wash, eventually passing northeast of Cerro La Sandia, on the lower slopes and bajadas. Descending into a broad valley, which eventually, by a circuitous route, drains into the Bahia de Los Angeles, the old trail proceeds northwestward, over a low divide, to an intermittent water hole east of Cerro Paraiso. Here, the trail forks again. One branch goes northward, along the lower slopes of the Sierra San Borja, east of Cerro San Borja, and joins an old mule trail which goes from Mission San Borja eastward to Bahia de los Angeles.

The other branch goes northwestward, onto the lava cap of the granitic sierra, passes through an uninhabited ranch site (possibly once known as San Gregorio), and descends to Mission San Borja, joining another mule trail just south of the mission.

The second group of trails (2 in Fig. 11) goes northwestward from Mission Santa Gertrudis, over rolling sparsely vegetated ground and along gravel-filled washes to a point slightly north of the forks of Arroyo San Luis. Here, they turn northward, up the west fork (Arroyo Tres Palmas) to a point west of Cerro La Sandia. The main group of trails here leaves the arroyo, and climbs northwest-ward over the granite basement of the Sierra San Borja, eventually reaching the lava cap of the range. Continuing roughly northwestward, the trail skirts and crosses several small arroyos, then dips deeply into and out of Arroyo Paraiso, which is more than a mile wide and a quarter of a mile deep. From this crossing, the trail trends toward the north to reach Mission San Borja. There are several “cutoffs” and alternate routes along this trail.

At the bottom of Arroyo El Paraiso are some crude ranch buildings, showing several cycles of construction; and a cattle trail runs southwest down canyon, connecting several water holes. This area, according to some local -reports, was used as a pasture in missionary days, and is still used as range at times.

The third group of trails (3 in Fig. 11) goes westward from Santa Gertrudis to El Arco, then trends northwestward, along the lower slopes of the Sierra San Borja, largely east of the 1970 unpaved “main road”, to the vicinity of San Borja, where it joins a complex of improved trails which connected the mission with various visitas.

Although convincing documentation is lacking, and local reports are somewhat sketchy, depth of wear and amount of improvement of these old trails furnish some clues to the order of their construction. It is apparent that the central trail (2 in Fig. 11) was the first built and most extensively used. Probably because of the barrier imposed by the Arroyo Paraiso, other trails were scouted, and the eastern trail (1 in Fig. 11) was improved for some miles southeast of San Borja. Work on this trail was never completed, perhaps because of the Jesuit Expulsion. Because he made a very fast journey from Santa Gertrudis to San Borja, and makes no mention of crossing Arroyo Paraiso, it is quite possible that Serra used this trail on his northward journey.

The third group of trails (3 in Fig. 11), except for the northernmost few miles, near San Borja, are probably not mission trails at all, but served to connect various prospect holes and small mines on the west side of the Sierra San Borja, after about 1840. Small sectors of these trails are still travelled by local ranchers, but, as they are unsuited for wheeled vehicles, they are seldom used today for extended journeys.

Mission San Borja is the end of the much-used Jesuit trail. For areas northward, we have a few accounts, largely by Father Linck, as well as the expedition records. The trail from San Borja to the water hole of Jubay is fairly direct, and somewhat resembles Linck’s return itinerary from his 1766 expedition. There are several other old trails in the vicinity, and, contrary to widespread accounts, there are perhaps a dozen water holes along this trail-some nearly permanent, some seasonal, some potable, and some perhaps dangerously mineralized.

From Yubay to Calamajue the trail winds through low hills, trending northwest, and gradually descending to the unsuccessful mission site at Calamajue. Leaving Calamajue northwestward, the trail goes between low hills and through shallow dry watercourses to Santa Maria, where the expedition received much needed supplies from a ship anchored in Bahia San Luis Gonzaga.

Northwestward between Santa Maria and San Fernando de Velicata, the expedition trail approximated the alignment of the old very much unimproved road. Travel here was from one palm-fringed “oasis” to another, with no serious problems of water shortage or trail difficulty.

After the founding of Mission San Fernando de Velicata, on May 13, 1769, the Serra party went roughly northward, up open valleys and over low hills, to San Juan de Dios. Although the map positions for Velicata and San Juan are “Government Official” as of 1973, there seems to be a longitude error here, as San Juan is roughly north-northeast of Velicata.

The last sector of the trail, from Velicata to San Diego, is shown by Fig. 12. At San Juan de Dios, Father Serra’s badly infected leg troubled him so severely that he doubted his ability to ride on. With the assistance of a hot poultice compound made and applied by the muleteer Juan Antonio Coronel, the leg improved overnight, and Serra was able to continue. What change in the course of history would a few milligrams of penicillin have made at this point?

Following what they thought was the trail of Father Linck, whose diary Serra had with him, the party followed a circuitous route slightly west of north, among the foothills of the Sierra San Pedro Martyr. Although Serra’s La Cieneguilla is at or near the point where Linck turned west to cross the Sierra, the route followed agrees only vaguely with that described by Linck. As the Serra Expedition reports contain much information, supposedly quoted from Linck’s diary, that is not in the recently published diary, it seems highly probable that a parallel Linck diary existed at one time.

As the expedition proceeded northward beyond San Fernando, an increasing number of Indians deserted, and more and more of the soldiers and aides became sick. Northwest of La Cieneguilla, the interpreter, Valladares, died, and was buried in an arroyo now named for him. Due perhaps to a combination of fatigue, hunger, and bad water, most of the expedition accounts become increasingly vague and contradictory north of La Cieneguilla. We are fortunate in having the diary of Jose de Canizares to guide us on this last part of the journey. Although the route shown here differs in some details from the Thickens and Mollins itinerary, the differences are largely due to use of a different, and it is hoped better, base map.

A short distance north of Arroyo Valladares, the Serra party turned slightly south of west, into the valley of San Telmo, followed that valley seaward for some miles, then turned roughly parallel to the coast again. The northwestward route followed in general the seaward slopes of the peninsular hills, keeping on good going and good grass, avoiding the relatively barren shore area, and deviating frequently in search of water.

From Ensenada to the present international boundary, the Serra route approximated the 1920 highway, crossing the present border between the present city of Tijuana and the International Boundary Marker. The Serra Party arrived in San Diego on July 1, 1769, the expedition being a success, but the personnel were sadly reduced by death and desertions.

Very shortly after the founding of San Diego, probably before 1782, the rough trail between San Fernando de Velicata and San Vicente, over which the Serra parties struggled so painfully, was abandoned as a main travel route, and replaced by a much easier trail, closer to the coast, and approximating the routes of the 1970 “improved road” and present (1975) Mexican Route 1.

This, in highly condensed form, is a summary of the problems of the Serra journey from Loreto to San Diego, and a reconstruction of the route using the best data available up to 1974. There are still a number of uncertainties, ambiguities, and contestable points, so that this paper should not be regarded as the final answer to the problem, but only as, it is hoped, a better answer. If, by disagreeing, or by uncovering new evidence, you can produce a better approximation, blessings upon you!

Acknowledgments: During the progress of this work, assistance has been received from many sources, both in the United States and in Mexico. The help so generously given by a variety of Mexican citizens, whose categories range from department heads in Mexico City to individuals in isolated ranches whose names are not yet on the map, is here most gratefully acknowledged. In the United States, valuable help and information was given by the Army Map Service, the U.S. Navy Hydrographic Office, the National Aeronautical and Space Administration, and especially by the U.S. Geological Survey, whose offices in Washington, Denver, Menlo Park, and Flagstaff have given assistance surely “far beyond duty requirements.”



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Herbert Bolton, Fray Juan Crespi, Missionary Explorer on the Pacific Coast, 1769-1774 (Berkeley, University of California Press, 1927).

Herbert Bolton, Historical Memoir of New California by Fray Francisco Palou, O.F.M. (Berkeley, University of California Press, 4 Vols. 1926).

Herbert Bolton, Rim of Christendom (New York, Macmillan, 1936), pp. 182-190.

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Ernest Burrus, Wenceslaus Linck’s Reports and Letters, 1762-1778 (Los Angeles, Dawson, 1967). Harry Crosby, The King’s Highway in Baja California (San Diego, Copley, 1974).

Peter Dunne, Black Robes in Lower California, (Berkeley, University of California Press, 1952), pp. 321-333, 380-387. Zephyrin Englehardt, The Missions and Missionaries of California, Vol. 1 (Santa Barbara, Santa Barbara Mission, 1929), pp. 80-552.

Maynard Geiger, The Life and Times of Junipero Serra, (Washington, Academy of American Franciscan History, 2 Vols. 1959), Vol. 1, pp. 200-244.

Peter Gerhard and Howard Gulick, Lower California Guidebook, Fourth Edition (Glendale, Clark, 1970).

George Hammond and Agapito Rey, Narratives of the Coronado Expedition, 1540-1542 (Albuquerque, University of New Mexico Press, 1940), pp.-210-212, 231-232.

Ronald L. Ives, “The Last Journey of Melchior Diaz,” Journal of Geography, 49 (February, 1960), pp. 61-66.

Ronald L. Ives, “Climate of the Sonoran Desert Region,” Annals of the Association of American Geographers, XXXIX (1949), pp. 143-187.

Ronald L. Ives, “Kino’s Route Across Baja California,” Kiva 26, (April, 1961) pp. 17-29.

Pablo Martinez, A History of Lower California, (Mexico, D.F., Editorial Baja California, 1960), pp. 106-270. Michael Mathes, First from the Gulf to the Pacific, (Los Angeles, Dawson, 1969).

Peveril Meigs, The Dominican Mission Frontier of Lower California (Berkeley, University of California Press, 1935). Richard Pourade, The Call to California (San Diego, Copley, 1968). Manuel Servin, The Apostolic Life of Fernando Consag (Los Angeles, Dawson, 1968).

Forrest Shreve and Ira Wiggins, Vegetation and Flora of the Sonoran Desert, 2 Vols. (Stanford, Stanford University Press, 1964).

Donald Smith and Frederick Taggert, “Diary of Gaspar de Portola During the California Expedition of 1769-1770,” Academy of Pacific Coast History, Vol. 1 (1909), pp. 33-89.

Frederick Taggert, “Diary of Miguel Costanso” Academy of Pacific Coast History, Vol. 11(1911) pp. 161-327.

Virginia Thickens and Margaret Mollins, “Putting a Lid on California: An Unpublished Diary of the Portola Expedition by Jose de Canizares,” California Historical Quarterly, XXXI, No. 2 (June, 1952), pp. 109-124; No. 3 (September, 1952), pp. 261-270; No. 4 (December, 1952), pp. 343-354.

Miguel Venegas, Noticia de la California y su Conquista Temporal y Espiritual (Mexico, D.F., Layec, 1944), pp. 91-120.


Ronald L. Ives teaches geography and borderlands history at Northern Arizona University, Flagstaff, Arizona. Education includes B.A. and M.S., Geology, Colorado, 1935 and 1937; M.A. and Ph.D., Geography, Indiana, 1947 and 1950. Numerous technical publications concerning geology, geography and history of western North America, 1931 to date. All illustrations, except above, courtesy of the author.