The railroad was chartered in 1905 by James J. Hill to connect the two transcontinental railroads owned by him, the Northern Pacific and Great Northern, to Portland, Oregon from Spokane, Washington, to gain a portion of the lumber trade in Oregon, a business then dominated by E.H. Harriman's Union Pacific and Southern Pacific railroads. Construction began in 1906 under the name Portland & Seattle Railway, proceeding eastward from Vancouver, Washington. 1906 also saw the start of construction of the line between Vancouver and Portland, including work on three major new bridges, crossing the Columbia River, the Oregon Slough and the Willamette River. The northernmost of these was the first bridge of any kind to be built across the lower Columbia River. Despite legal challenges from Harriman, within a year the line had been built as far as Pasco along the Columbia River, where it connected with NP. The first section to open was from Pasco west to Cliffs, a length of, on December 15, 1907. Operation was extended west to Lyle, further west, on January 15, 1908, as construction continued on the section from Pasco to Vancouver. In January 1908 "Spokane" was added to the railroad's name, making it the Spokane, Portland & Seattle Railway. SP&S freight and passenger service to Portland was inaugurated in November 1908. By 1909 the railroad had completed construction of its line up to Spokane along the Snake River. In 1910 SP&S gained control of the Oregon Electric interurban railway, which the Great Northern had acquired two years before. Under the control of the SP&S the railroad was extended southward to Eugene by 1912. SP&S also operated a second subsidiary railroad in western Oregon, the Oregon Traction Company, which owned a route to Seaside. A third route on which the SP&S operated extended southward from Wishram, Washington, to Bend, Oregon, was the Oregon Trunk Railroad. Edward Harriman's Oregon & Washington Railway & Navigation Company also was building a railroad south from the Columbia River to Bend resulting in a railroad war in which each railroad attempted to sabotage the other. In the end, the railroad opened using mostly the track of the Oregon Trunk, with a short portion of the Oregon & Washington Railway & Navigation Company track, and both railroads used the route. During World War II the SP&S carried war materials to the Pacific Theatre; new industries located along the Columbia River, taking advantage of cheap electricity from hydroelectric dams on the river. New industries served by the SP&S included aluminum plants, sawmills, chemical factories and grain elevators. In 1954, a SP&S train derailed after hitting a rockslide on the route to Bend, Oregon, killing all crew members. Part of the train landed in the Deschutes River, including a boxcar, which landed in a rapid that was later named "Boxcar Rapids" after the incident.
Passenger trains
The SP&S's passenger operations mostly involved hosting connections with parents' trains, such as the Empire Builder and North Coast Limited, which were combined to form the Streamliner. Oriental Limited, Mainstreeter, and Western Star connected with. However, some of these SP&S trains were named. The Inland Empire Express and North Bank Limited provided daily, through service between Portland and Spokane. The Columbia River Express operated between Portland and Pasco, connecting at Pasco with Northern Pacific #5/#6 for service to/from Spokane.
