Reporting mark OSL
Locale Idaho, Montana, Oregon, Utah & Wyoming
Dates of operation April 14, 1881-1987
Length 321 miles (517 km)
The Oregon Short Line Railway was organized on April 14, 1881. The line started from the Union Pacific main line in Granger, Wyoming, and reached Montpelier, Idaho, on August 5, 1882, and then to McCammon, Idaho, in the Fall of 1882. Between McCammon and Pocatello, Idaho, the line was shared with fellow Union Pacific subsidiary Utah & Northern's grade by adding a third rail to the 3 ft (914 mm) narrow gauge track to accommodate the 4 ft 8+1⁄2 in (1,435 mm) standard gauge cars. The line from Pocatello to Huntington, Oregon, was completed in late 1884. Access to Portland, Oregon, was on track leased from the Oregon Railway and Navigation Company.
The line was essential because the Union Pacific main line ended in Utah where it met the Central Pacific Railroad, which by that time was part of the Southern Pacific Railroad. The Southern Pacific had built tracks as far east as El Paso, Texas, and would, in 1883, become a transcontinental railroad in its own right. The Southern Pacific then started routing traffic to the southern line, cutting off the Union Pacific, which needed other access to the Pacific coast. The Oregon Short Line also was meant to halt the OR&N's continued eastward expansion at the Idaho-Oregon border.
The OSL was independent for a short period of time until October 1898 when the newly reformed Union Pacific Railroad took control of a majority of the board of directors. During the early part of the 20th century the railroad publicized tours of Yellowstone National Park by way of a spur constructed from Idaho Falls, Idaho, to West Yellowstone, Montana. In 1938, Union Pacific began consolidating operations and leased for operation a number of its subsidiaries including the Oregon Short Line. The railroad operated under the lease until December 30, 1987, when the OSL was fully merged into the Union Pacific Railroad.