After 1800, the vicinity of Mesilla was a camping and foraging spot for both Spaniards and Mexicans. It wasn't until after the treaty of Guadalupe
Hidalgo in 1848 that the first permanent settlers came to Mesilla to make it their home. By 1850, Mesilla was a firmly established colony. The constant threat of attack by the Apache
put these early settlers on constant alert. Apaches periodically swept through the Mesilla area, stealing livestock and foodstuffs, murdering
colonists and seizing captives. Just as frequently the villages swiftly retaliated by sending out the Mesilla Guard, a militia comprised of a man
from each household. Time after time the militia wrought revenge on any Apache in the area. In 1851, Apache depredations in the Valley caused
the United States government to establish Fort Fillmore to protect the newly conquered territory and its people. As a result of the Mexican War
and the Treaty of Guadalupe Hidalgo, Mesilla was within the strip of land claimed by both the United States and Mexico, a "no mans land".
In 1854, the village, being closer to the fort than either Las Cruces or Dona
Ana, became the supply center for the garrisoned troops, providing entertainment, food, hay and building materials. The Mexican inhabitants of
Mesilla also provided the knowledge needed to build a fort of adobe. The colony of Mesilla flourished. It was a major stop on the crossroads of the
Chihuahua Trail, and now the fort demanded items Easterners were accustomed to having. Business prospered and Anglo merchants such as
Fountain, Reynolds, Griggs, and Bean, many of whom had come with the first armies were among those who reaped the profits of commerce. In
1854, The Gadsden Purchase declared Mesilla officially part of the United States. As Mesilla was the most important community in this parcel, the
treaty was consummated by the raising of the American flag on the town plaza with much ceremony on November 16, 1854.