Old Mesilla was a busy trade center for Mexico. The portion north of old Mesilla was claimed by Texas when they seceded from Mexico claiming New Mexico and other lands including Colorado and Wyoming. The area changed little until the US Army claimed the territory in 1846 as part the United States versus the claim of Texas. Mexicans unhappy with this moved back to Mexico and primarily Old Mesilla just across the Rio Grande river. Southern states wanting a direct rail route to the Pacific were the force behind the Gadsden treaty giving old Mesilla back to the US. It became an important stagecoach route and later train route on the Southern Pacific railroad. Lot of history in this old town which remain true to its culture and architecture.