El Camino Real de Tierra Adentro

This old road starts in Mexico City.

It goes north, a very long way, all the way to the United States.

El Camino Real de Tierra Adentro means the Royal Inland Road. It is also called the Silver Route. The road ran about 2,600 kilometers north from Mexico City to Texas and New Mexico, in today's United States.

It is not one building but a long line of places. UNESCO lists 60 of them along a 1,400-kilometer stretch in Mexico: bridges, old farm estates called haciendas, towns, stretches of road, a mine and caves.

UNESCO's serial World Heritage property, inscribed in 2010, links 55 sites and five existing World Heritage sites (among them Mexico City, Querétaro, Guanajuato and Zacatecas) along a 1,400 km stretch between Mexico City and the town of Valle de Allende in Chihuahua.

In the United States, the National Park Service says the road descended the Rio Grande Valley from north of Santa Fe and passed through the natural gateway at El Paso on its way south. Part of the old route in Mexico is now part of the Pan-American Highway, ICOMOS notes.

Mules pulled wagons full of goods along the road.

Each wagon had eight mules!

The National Park Service says caravans on the road usually had 32 wagons. Eight mules pulled each wagon, and each carried about 4,000 pounds of goods. Most caravans also brought cattle, sheep, goats, donkeys and chickens.

The wagons carried mail, royal orders and goods to sell. Silver went one way, and mercury, needed to process the silver, came the other way.

Mercury, needed to process silver by the 'amalgamation' method, was imported from Spain and at times from Slovenia (ICOMOS). The National Park Service describes caravans of typically 32 wagons, each hauled by eight mules with about 4,000 pounds of freight, plus livestock such as cattle, sheep, goats, burros and chickens; royal decrees, mail and private merchandise made up the freight.

UNESCO says the silver led to massive economic development in Spain and other parts of Europe, and a period of great inflation.

This photo shows a river winding through a green valley, with mountains far away.

The old road passed through land like this.

This photo was taken on 29 July 2012 by the Bureau of Land Management, which helps look after the trail in the United States. It shows a winding river, thick green trees, fields and faraway mountains.

In the United States, the route is a National Historic Trail. You can follow its general path on modern highways in New Mexico and Texas, but many miles cross private land.

The photograph (Bob Wick, Bureau of Land Management, 29 July 2012) was published to illustrate El Camino Real de Tierra Adentro National Historic Trail; its caption does not name the place. It shows a winding river with several channels in a wooded valley below farmland and distant mountains.

The BLM and the National Park Service administer the U.S. trail, and many of its most important sites are privately owned or managed by tribal, state or city agencies. In Mexico, the National Institute of Anthropology and History (INAH) and the ten states concerned manage the World Heritage sites.