While the legislated El Camino Real de Tierra Adentro National Historic Trail extends 404 miles in Texas and New Mexico, the historic trail extended all the way to Mexico City. There are museums, historic sites, churches, and original trail segments located all along the length of the trail into Mexico.
To assist with your trip planning, contact information and locations of some trail-related sites and museums can be found at Places to Go in New Mexico and Places to Go in Texas.