By Tom Morrow

Looking at the map today of the Southwestern United States, approximately one-third of the lower part of Arizona and a portion of southern New Mexico was the last parcel added to the contiguous 48 states by what was known as the “Gadsden Purchase” from the Republic of Mexico.
In that $15 million Land transaction of 1853, the United States also came very close to possessing the entire peninsula of Baja California. But that would have cost the U.S. an additional $50 million for Baja if it was added to the territorial portions of the northern Mexican states of Sonora and Chihuahua. The Gadsden Purchase consisted of a 29,640 square-mile region of present-day southern Arizona and southwestern New Mexico.
The treaty was signed on Dec. 30, 1853 by James Gadsden, who at the time was the ambassador to Mexico. The treaty also served to reconcile outstanding border issues between the U.S. and Mexico emanating from the 1848 Treaty of Guadalupe Hidalgo, which ended the war with Mexico.
The treaty, known in Mexico as the “Sale of La Mesilla,” was primarily negotiated to provide right-of-way for U.S. transcontinental railroads. The war had left Mexico heavily in debt. Yankee dollars were sorely needed by Mexican President Santa Anna, who wanted to rebuild his army out of fear the Americans would attack again.
The Gadsden Purchase was ratified, with changes, by the U.S. Senate on April 25, 1854, and signed by President Franklin Pierce, with final approval taken by Mexico’s congress on June 8, 1854. The purchase included lands south of the Gila River and west of the Rio Grande, which make it possible for the U.S. to construct a transcontinental railroad with a southern route. Pre-Civil War business-oriented Southerners saw such a transcontinental railroad linking the southern U.S. states with the Pacific Coast, which would expand their trade opportunities.
However, many in Washington thought the topography of the southern portion of the original boundary line to the 1848 Mexican ceded territories, (California, Nevada, Utah, Arizona, New Mexico, western Colorado) were too mountainous to allow such a direct rail route.
President Pierce’s administration, strongly influenced by Secretary of War Jefferson Davis, had seen an opportunity to acquire land for the railroad by adding a significant amount of territory from northern Mexico. However, controversial debate in Washington, D.C., developed over the treaty which evolved into a North-South dispute over slavery. Would the newly-acquired territory be allowed slavery?
After the treaty was approved by both countries, a survey party was designated to officially establish the border. The joint American-Mexican survey party surveyed and mapped the Gadsden Purchase border from the Pacific to El Paso. With that party was U.S. Army surveyor Lt. Cave Couts. He would later be one of the first white settlers to develop a vast Rancho Guajome located in what today is northern San Diego County. The surveyor’s transit Couts used was, for a time, on display at the County’s Rancho Guajome museum in Vista.
Today, the Gadsden Purchase and the Treaty of Guadalupe Hidalgo have been nearly forgotten, but both are important aspects of American history. Our southern border would look very different today without the Gadsden Purchase, but how very different it would look if Baja California had been included in that treaty?

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