The Chile Line
The roots of the Los Alamos Northern Line Railroad dates back to the Denver & Rio Grande days with the Santa Fe branch from Antonito, Colorado down south to Santa Fe, New Mexico. Originally narrow gauge, the line was never profitable and faced abandonment in the early days of operations.
The line found resurgance around the 1940s with the creation of the secretive Manhattan Project, which would develop the first nuclear weapons. The line between Santa Fe and Otowi was converted to standard gauge with the branch line constructed off of the main line and between the mesas towards Los Alamos National Laboratory.