From Spanish capital to Spanish capital the Camino Real de Tierra Adentro ran from Mexico City, Mexico to Ohkay Owingeh, New Mexico. The portion of the Camino Real in New Mexico is about 404 miles beginning in El Paso running northward parallel in some areas by I-25. The camino was formally established as the royal road or Camino Real by Juan de Onate in 1598.

There were two other royal roads:

• Going westward from Mexico City to Tucson and on to San Francisco sometimes associated with Calle Real (within the US state of California), usually refers to the historic 600-mile road (US Route 101) connecting the 21 Spanish missions in California.
• The El Camino Real de los Tejas covers the modern highwaysTexas 21 (along with Texas OSR) and Louisiana 6,roughly follow the original route of the trail. The trail has a 2,500-mile length from Mexico City to the US in Laredo, San Antonio, to Nacogdoches.

For centuries the Native Americans had used the trail routes for trading between the Great Plains and Chihuahuan Desert regions. The Caminos Real first followed and marked by Spanish explorers and missionaries in the 1700s.

The trail was nationally significant for its use in conquest, colonization, settlement, missionary work, supply, commerce, cultural exchange and military campaigns.

The first breeding horses, cattle and sheep entered New Mexico and the American West was through the Camino Real as did gun powder, written language, iron, and Christianity. The road also served as a lifeline for the new Spanish immigrants for continued supplies from Mexico and Spain such as fine cloth and spices.