Spokane, Portland and Seattle Railway

The railroad was chartered in 1905 by James J. Hill to connect the two transcontinental railroads owned by him, the Northern Pacific (NP) and Great Northern (GN), 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 to the east and south from Vancouver, Washington. The work included construction of three major bridges over 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 (near Maryhill), a length of 112 miles (180 km), on December 15, 1907. Operation was extended west to Lyle, 33 miles (53 km) further west, on January 15, 1908, as construction continued on the 221-mile (356 km) section from Pasco to Vancouver.

In January 1908 "Spokane" was added to the railroad's name, making it the Spokane, Portland & Seattle Railway. A "golden spike" ceremony was held on March 11, 1908 at Sheridan's Point to commemorate the completion of the railroad along the Columbia. SP&S freight and passenger service (from Pasco) to Portland was inaugurated in November 1908. (First & Second Subdivisions) By 1909 the railroad had completed construction of its line up to Spokane along the Snake River (Third Subdivision).

In 1910 the SP&S gained control of the Oregon Electric interurban railway, which James J. Hill and the Great Northern had acquired two years before. Under the control of the SP&S (Ninth, Tenth, & Eleventh Subdivision), the railroad was extended southward to Eugene by 1912. The line was extended from Albany into Lebanon, Oregon, and Sweet Home, Oregon, in 1931. The Dollar branch was completed from Sweet Home to Dollar, Oregon, later that same year.

SP&S also operated a second subsidiary railroad, which James J. Hill purchased in 1907 for 5 million dollars, in northwestern Oregon. This was previously the Astoria and Columbia River Railroad, which created a route in 1898 along the south bank of the Columbia River, from Portland through to Astoria and Seaside. This portion of the SP&S (Sixth & Seventh Subdivision) was known as the "Astoria" or "A" line.

A third route on which the SP&S operated extended southward from Wishram, Washington, to Bend, Oregon, was the Oregon Trunk Railway Company (Fifth Subdivision). Edward Harriman's Oregon Railroad and Navigation Company also was building a railroad south from the Columbia River to Bend resulting in a "railroad war" across opposite sides of the Deschutes River 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 (an arrangement that still exists with BNSF owning the majority of the line and UP having trackage rights). Building this railroad included construction in 1912 of another railroad bridge across the Columbia River, the Oregon Trunk Rail Bridge, at Wishram, Washington.

The 41 mile branch to Goldendale (Fourth Subdivision), the only branch line in Washington State, began at Lyle Washington. This railroad was originally completed in 1903 as the Columbia River & Northern Railway and was quickly acquired by the SP&S after the 1908 completion along the north bank of the Columbia River. This branch was shut down in 1992.

United Railways later became a branch line of the SP&S (Eighth Subdivision). The finished United Railways line went north from Wilkesboro through Banks, Manning, Buxton and Vernonia, Oregon. At this location, the line turned west, eventually reaching the town of Keasey, and continued on to the county line between Clatsop and Columbia Counties. Several logging companies started operation in the area, and used the United Railways to some extent. However, Oregon American traffic continued to be the largest user of the line. In 1944, the United Railways was dissolved and taken over completely by the Spokane Portland & Seattle Railway. In 1953, the line was sold to Long-Bell Lumber Company and in 1956 Long-Bell was sold to International Paper. International Paper had different plans for the region, and by September 1957 the rail traffic was gone. The line from Vernonia westward was abandoned in 1958.