Society for the History of Discoveries

Rebert, Paula.  La Gran Línea:  Mapping the United States-Mexico Boundary, 1849-1857. Austin: University of Texas Press, 2001. 259 p. ISBN 029277110X

     The purported several million Mexicans illegally in the United States are of concern and, for some, a threat to the country’s linguistic homogeneity. How far does a country such as the United States go in securing its borders without negatively impacting its long tradition as a nation comprised in no small part of immigrants? Borders, to be sure, have meanings to different people.

     Paula Rebert takes us back to another time in Mexican-American relations. It was shortly after the war of 1848 when a victorious United States and defeated Mexico sought to define the new boundary between the two countries where the one had lost nearly one-half of its national territory and the other gained enormous expanse of new land. Where one might have expected the defeated to procrastinate in establishing the new demarcation, the opposite occurred. In spite of its weak financial resources and burdened with the stigma of military defeat and deprivation of its motherland, it was Mexico perhaps more so than the United States that sent forth its best and brightest technicians. Their task as with the Americans was to place markers on the ground and lines on maps defined by latitude, longitude, triangulation often through use of signal fires, celestial observations and all other available mapping techniques in a frontier region of inhospitable terrain and generally lacking in amenities and natural resources. The most up-to-date measuring devices were obtained and deployed often at considerable expense (especially by the Americans who had deeper pockets). This was done over a period of several years and in 54 final maps based on scores of preliminary maps prepared by each commission. In some stretches of the border, only one map was prepared and accepted as definitive by both national commissions. Not content with having acquired through force of arms nearly one half of Mexico, it was the Americans who sought the greatest territorial advantage through modification of some of the surveys! Finished maps reside in the national archives of the two countries.

     In an era of satellite communications where locations on the earth’s surface can be measured to the nearest 15 meters or less, it is difficult to envision the tasks faced by the field personnel engaged by the two national commissions. Field drawn maps, cartographically accurate but sometimes based on different reference points, were submitted to both commissions, then compared for possible revision and eventual joint acceptance. Final cartography took place in Washington, D.C. rather than in Mexico, due in the main to the inability of the Mexican Government to support its personnel financially to the extent that the Americans were supported by their government. This is a story of the leading personalities, the three divisions of the boundary survey from Matamoros to San Diego Bay and the problems and solutions to the drawing of the boundary line.

     The Treaty of Guadalupe Hidalgo (Treaty of Peace, Friendship, Limits, and Settlement) signed on February 2, 1848 among other things called for government commissions to survey, agree upon and demarcate the actual border. Maps have faults and those employed by the American treaty negotiators to define the outlines of the anticipated land grab were no exception. The Rio Grande also was a problem in that the river was not navigable and the Thalweg at times impossible to determine. Mutually understood and acceptable cartographic reference points were a constant problem. Nevertheless, and possibly the most remarkable component of the mapping enterprise besides the overcoming of physical handicaps, was how mutually accommodating were the commissioners and technicians in scientific matters. This was especially true for the Mexicans who won the admiration of their American counterparts while undertaking what might well have been for some a rancorous task. Agreements to settle different national interpretations of local variation were the rule rather than the exception. Whereas the treaty was political, the drawing of the boundary line was a technical exercise seldom encumbered by overly contentious political issues.

     The three mapping sections for the boundary line were from the mouth of the Rio Grande to El Paso del Norte, the Sonora Desert and from the Gila River to San Diego Bay. Surveying occurred in each section often independent of work elsewhere. The two end points of San Diego Bay and the Rio Grande at Matamoros received considerable attention but a mutually acceptable reference point on the upper Rio Grande proved to be contentious. The treaty negotiators (Mexican; 7th edition) and (American; 12th edition) used different editions of John Disturnell’s Mapa de los Estados Unidos de Méjico. Disturnell placed the Rio Grande too far to the east and Paso del Norte (now Ciudad Juárez) too far to the north. These errors were to bedevil the surveyors and cartographers. Also contentious was the point of contact at the Gila River following a survey from San Diego Bay and the location downstream on the Colorado River where the boundary shifted from one drawn from west-to-east to one southeasterly in direction through the Sonora Desert. Where exactly one stream made contact with another was open to varied yet well meaning interpretation. Meandering, braided streams were the norm whereas deep and clearly defined channels were the exception. The few and widely scattered settlements sometimes proved to be as elusive as use of streams for fixed reference points. Cartography concentrated on the border line and maps invariably contained emptiness elsewhere unless there was a particularly significant physical feature. Thirty-six maps are reproduced for this study and, while informative, generally are difficult to read, at least with ease. Some of the originals housed in the National Archives are in poor condition.

     This is a fascinating story of a near forgotten past when politics and war gave rise to a prodigious mapping project that, in retrospect, causes one to question whether it was worthwhile in the first instance. This, however, is beyond Rebert’s brief and she is to be congratulated for a good and well documented story.

William R. Stanley
University of South Carolina, Columbia

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