The United States Army Establishes Fort Buchanan On Sonoita Creek
The purchased lands were initially appended to the existing New Mexico Territory.
To help control the new land, the United States Army established Fort Buchanan on Sonoita Creek in present-day southern Arizona on November 17, 1856. The difficulty of governing the new areas from the territorial capital at Santa Fe led to efforts as early as 1856 to organize a new territory out of the southern portion of the New Mexico Territory. Many of the early settlers in the region were, however, pro-slavery and sympathetic to the South, resulting in an impasse in Congress as to how best to reorganize the territory.
# Gadsden Purchase of 1853, United States purchased a strip of land along the U.S.-Mexico border for $10 million, now in New Mexico and Arizona. This territory was later used for the southern transcontinental railroad.