Railroad Bridges Over the Pecos A major tributary of the Rio Grande, the Pecos River was long a barrier to transportation, particularly across the deep gorge that once marked its joining with the Rio Grande. Construction of the first railroad bridge over the Pecos took place in 1882 as part of the transcontinental route of the Southern Pacific Railroad across the lower portion of the United States. Access to the bridge, which was then deep in the canyon, was by means of a circuitous route and two tunnels. In 1890, Southern Pacific officials began planning for a new bridge, one that would cut directly across the ravine by means of a high-line viaduct that would save miles and straighten the route. Work began in late 1891 and was completed within three months at a cost of more than $250,000. Supported by 24 towers, the bridge was the highest in North America and the third highest in the world at the time of its completion. Passenger trains slowed to six miles per hour before crossing it and stopped while on the bridge to afford travelers a view. During World War II, the Pecos High Bridge became essential to the transportation of war materials. In response to heavier trains and the war demand, a new bridge was built in 1944, with special permission from the War Production Board to use "critical materials" in its construction. The 1944 Pecos High Bridge remains in use, although the gorge is not so deep as it once was, due to the rising of the river with the construction of Amistad Reservoir.