FROM THE GOLDEN GATE
TO MEXICO CITY

THE U.S. ARMY
TOPOGRAPHICAL
ENGINEERS IN THE
MEXICAN WAR, 1846 1848

by
Adrian George Traas

OFFICE OF HISTORY, CORPS OF ENGINEERS
and
CENTER OF MILITARY HISTORY

UNITED STATES ARMY
WASHINGTON, D. C., 1993

Traas, Adrian George, 1934-
From the Golden Gate to Mexico City: the U.S. Army Topographical
Engineers in the Mexican War, 1846-1848 / by Adrian George Traas.
p. cm. - (CMH pub; 70-10)
Includes bibliographical references and index.
1. Mexican War, 1846-1848-Engineering and construction.
2. United States. Army. Corps of Topographical Engineers-History.
3. Mexican War, 1846-1848-Regimental histories-United States.
4. Military Topography-United States-History-19th century.
I. United States. Army. Corps of Engineers. Office of History.
II. Center of Military History. III. Title. IV. Series.
E409.2T73 1992
973.6'24-dc20
91-45500
CIP

CMH Pub 70-10

First Printing

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402

Foreword

In performing its many civil-military missions throughout its history, the U.S. Army has often been a pioneer on the frontiers of technology. Army engineers in particular have been preeminent in developing and using new technologies to carry out their assignments. Even predating their organization into a separate branch in 1838, the Army's topographical engineers carried on civil works programs, their work in road and harbor construction, waterway charting, and all the great innovations involved in creating a continental infrastructure quickly elevating them into a kind of quasi-independent federal civil works organization. Prominent among these missions was the exploration and mapping of the West.

Mapping in nineteenth century America had both a civilian and military dimension. Military and civilian explorers mapped the territories of the American West, providing one of the essential tools for agricultural expansion and urban development. As part of their traditional military responsibilities, Army engineers accompanied military forces in the field, making reconnaissances, planning the route of advance, and charting the terrain for the military commanders. Commanders also looked to the engineers for special kinds of intelligence involving the terrain and the military strength of the enemy.

Topographical Engineers in the Mexican War serves a twofold end. The book demonstrates how the engineers performed a valuable combat support mission in America's first foreign war. It describes their contribution to the Fremont and Kearney expeditions to California and their efforts during General Zachary Taylor's advance to Buena Vista. It also shows the engineers on the cutting edge of nineteenth century technology as they laid the communication routes throughout the southwest and California that would tie the new continental nation together.

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In addition to the intrinsic interest found in an account of such adventures, today's military students can also learn much about the influence of terrain on campaigns and battles, encountering principles that still govern the use of geographical intelligence in our era of computer and satellite technology. What follows should also renew their pride in the knowledge that the Army has always stood on the forefront of science and technology during its two centuries of service.

Washington, D.C.
7 June 1991

[iv]

The Author

Lt. Col. Adrian G. Traas, U.S. Army Corps of Engineers, retired, received his commission and B.A. degree upon his graduation from Marquette University in 1957. He received a Master of Arts degree in history from Texas A&M University in 1971.

His military service included assignments as executive officer and commanding officer of the 64th Engineer Battalion (Base Topographic) in Italy, Ethiopia, Liberia, and Iran; staff officer and instructor at the Army Engineer School; professor of military science at Marquette; and assistant chief of Histories Division at the Center of Military History. He has also served as company commander of engineering units in Korea and Fort Belvoir, Virginia; as post engineer in Italy; and on ROTC duty at Texas A&M. He served two tours in Vietnam, the first with the 19th Engineer Battalion and 45th Engineer Group and the second as an adviser with a South Vietnamese engineer group and a deputy region engineer.

He is currently preparing a volume on military engineering operations in the Vietnam War series.

[v]

Preface

This publication analyzes and explains the role of the U.S. Army Topographical Engineer Corps in the war with Mexico, commencing with the activities of the Topographical Engineers in 1845 and tracing their evolution from a scientific, mapping, and construction agency of the federal government to their active participation in the war. Originally submitted as a master's thesis at Texas A&M University, the account begins with the role the Topographical Engineers played in military reconnaissances and explorations in anticipation of the hostilities between the United States and Mexico. Their role during the war is recounted, particularly the conquest and explorations of California, New Mexico, and Arizona. Included is Capt. John C. Fremont's third expedition, important for both its military and geographic contributions. Under the commands of Generals Scott and Taylor in Mexico, several officers of the corps assumed important leadership responsibilities in addition to their topographic duties. They contributed to the American military victory, and, of more lasting consequence, their reports provided basic scientific information about the little-known regions that became part of the United States as a result of the Mexican War.

The Corps of Topographical Engineers, or more informally identified as "topogs," was established as a separate corps in 1838, when some thirty-six authorized officers were placed on an equal footing with the Corps of Engineers. Their responsibilities were topography, mapping, and civil engineering works authorized by Congress. This realigning left the larger Corps of Engineers free to concentrate on its combat role as supporter of the Army in the field and builder of coastal fortifications.

The topographic responsibilities entailed exploring and surveying the territories on both sides of the Mississippi River. By 1845, John C. Fremont as a result of his second expedition, had

[vii]

pushed these explorations westward to California. The knowledge of the land and the scientific data that the Topographical Engineers brought back to Washington resulted in accurate mapping and provided information about people, plant and animal life, routes, minerals, and soil conditions.

Nearly two-thirds of the officers of the Corps of Topographical Engineers served with distinction in the Mexican War. Just as significant and more lasting were the results of their topographic and geographic studies. Even in the midst of a war, members of this scientifically oriented corps noted their geographic surroundings. The Topographical Engineers were as much at home in speaking before a group of scientists as in living in and exploring the rugged terrain or supervising boundary surveys, lighthouse surveys, river and harbor improvements, and construction projects. The efforts of this small corps of topogs resulted in more accurate maps of the newly acquired lands in the West and in portions of Mexico. The published travels of these officers, along with the other popular travel literature of the day, stimulated interest in westward migration.

This study outlines the activities of the Corps of Topographical Engineers and the diversity of its efforts in the only conflict in American history in which the corps served throughout as a distinctive branch of the Army. Because of the contribution of members of the Corps of Topographical Engineers, commanders were able to effectively use the reconnaissance information provided. These engineers played decisive roles in campaigns in California and Mexico, and provided the nation with maps of the newly acquired lands and vast amounts of valuable scientific findings.

In the course of research and writing the author has received generous support from many individuals. Deep appreciation and gratitude is extended to Dr. Herbert H. Lang, Texas A&M University, for his patient understanding in directing this research and his valuable suggestions for improving the style and form of this study when it was prepared in 1971. I am also most appreciative of the assistance rendered by Dr. Garry D. Ryan and other employees of the National Archives, and the constructive criticism of Drs. Allan G. Ashcraft and T.M. Stinnett, who graciously consented to serve on my thesis committee. A special word of appreciation is also due Mrs. E.I. Bailey for typing the original thesis manuscript and Mrs. Wyvetra B. Yeldell for her typing a portion of the initial revised

[viii]

manuscript for this publication. A word of thanks also goes to Dr. John T Greenwood, the former Chief of the Office of History, U.S. Army Corps of Engineers, who believed this study had some merit for publication. The study also benefited greatly from the advice of reviewers of the Engineer Office of History including Drs. Frank N. Schubert and Paul K. Walker and Mr. Dale E. Floyd. I am also indebted to the thorough review given by Lt. Col. Richard O. Perry, former Chief, Histories Division, U.S. Army Center of Military History, and Dr. Jamie W. Moore, the Citadel.

A special word of thanks is also due to Morris J. MacGregor, Acting Chief Historian, and to John W. Elsberg, Editor in Chief of the Center. A large amount of praise is also owed to the editors: Kathleen Richardson for the original manuscript and Samuel Duncan Miller for the final editing. Barbara H. Gilbert, Diane Sedore Arms, and Joycelyn M. Canery skillfully carried the manuscript through to publication. Arthur S. Hardyman, Howell C. Brewer, Sherry L. Dowdy, and Linda M. Cajka ably handled graphics and cartographic support.

Of course, the author alone is responsible for all interpretations and conclusions drawn in this work, as well as any errors that may occur.

ADRIAN G. TRAAS
Washington, DC
7 June 1991

[ix]

Contents

[xi-xiii]

Appendixes

Tables

Maps

Illustrations

The following illustrations wear between pages 50 and 62:

xiv

The following illustrations appear between pages 102 and 114:

The following illustrations wear between pages 164 and 176:

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page created 16 September 2002

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