• Northern Pacific - connecting to Columbia River lines in Pasco and Portland, providing the first Pacific Northwest connection to the rest of the railroad world.
• Spokane, Portland & Seattle - connections to Pasco, Spokane, and Seattle via bridges and a new main line on the north side of the Columbia River.
• Great Northern operated very few actual railroad lines in Oregon, but connected with Portland over other lines.
• Chicago, Milwaukee St. Paul & Pacific - one last gasp of life for this railroad in the Pacific Northwest included a connection in Portland.
• The Burlington Northern Santa Fe owns the lines from Portland north at this time.

• The Oregon and California Railroad - efforts at the first railroad in the Willamette Valley and Portland.
• The Southern Pacific - few cities in the Willamette Valley can mention their history without also mentioning the name of this company.
• Union Pacific - currently the important main line from Portland south into California is owned by this company.
• Great Northern built a line south from Bend. However, this history is really more a part of the Oregon Trunk.

• Portland Terminal and Northern Pacific Terminal, which operated the Portland Union Station.
• Portland Traction Company and its ancestors in Portland streetcar and interurban history.
• The Oregon Electric ran between Portland, Forest Grove, and Eugene, with branch lines to Sweet Home, Woodburn, and a few other places.
• The Oregonian was an early attempt at trying to compete with the Oregon & California in the Willamette Valley, as well as provide transportation to those cities that were being ignored.
• Willamette Falls Railway - see Portland Eugene and Eastern
• Crown Zellerbach had a narrow gauge industrial tramway at its paper mill just over the Columbia River in Camas, Washington
• Willamette Valley Southern between Oregon City, Molalla and Mt. Angel, with trains operating to Portland over the interurban line tracks. Late in life, the line briefly operated as the Willamette Valley Railway.
• United Railways operated one streetcar line, industrial trackage in Portland, and a logging and passenger line from northwest Portland to Banks, Vernonia, Keasey and beyond.
• Oregon Pacific and its operations in Portland and Canby.

Branch lines are short extensions operated by larger companies. Short lines are small railroad companies that are entirely their own operation, almost always with a connection of some sort to interchange traffic with another company.

The two major railroads operating branch lines through the area were:

• The Southern Pacific
• The Oregon Electric

• Oregon Central Railroad Company - the first attempt at operating a long-distance railroad in Oregon.
• Vernonia South Park and Sunset Stean RR, Inc. was the first attempt at starting a tourist railroad in Oregon. See United Railways
• The Carlton & Coast Railroad - serving the upper reaches of the North Yamhill River.
• Willamette Valley & Coast - a small company running to the community of Cherry Grove.
• Stimson Lumber Company - little documentation can be found about this line, which operated from the Stimson mill near Hagg Lake into the woods.
• United Railways operated one streetcar line, industrial trackage in Portland, and a logging and passenger line from northwest Portland to Banks, Vernonia, Keasey and beyond.
• Pacific Railroad & Navigation - eventually purchased by the Southern Pacific
• Portland Astoria & Pacific - see United Railways
• Gales Creek & Wilson River Railroad

Branch lines are short extensions operated by larger companies. Short lines are small railroad companies that are entirely their own operation, almost always with a connection of some sort to interchange traffic with another company.

The tiny portage operation at Oregon City was the first attempt to build a railroad-like means of transportation in Oregon.

• The Oregonian was an early attempt at trying to compete with the Oregon & California in the Willamette Valley, as well as provide transportation to those cities that were being ignored.
• Oregon Pacific and its operations in Portland and Canby.
• Willamette Valley Southern between Oregon City, Molalla and Mt. Angel, with trains operating to Portland over the interurban line tracks. Late in life, the line briefly operated as the Willamette Valley Railway.
• Independence & Monmouth Railway - operated on 2.5 miles of its own track between these two cities, 1890 to 1918. Up to 32 miles of track were operated due to rights over the Southern Pacific to West Salem, Dallas and Airlie.
• The Oregon Electric operated from Portland west to Forest Grove and south to Eugene. It was the largest railroad electrification effort in the history of the state of Oregon. It was part of the Spokane Portland and Seattle, later Burlington Northern, and now Burlington Northern Santa Fe.
• The Valley & Siletz Railroad operated from a point on the Willamette River near Independence to the city of Valsetz.
• The Willamette Valley Railroad operated a small part of the old V&S during the 1980's.
• The Willamina & Grande Ronde operated the line west from Willamina, before that was taken over by the Hampton Railroad.
• Portland Eugene and Eastern was involved in several railroads before being purchased by the Southern Pacific. Major portions included Corvallis to Eugene, an electric railway around West Linn, Canby to Molalla, Sheridan to Willamina, and several streetcar lines.
  • Willamette Falls Railway - see Portland Eugene and Eastern
  • Sheridan and Willamina Railroad - see Portland Eugene and Eastern
  • Corvallis and Alsea River Railway - see Portland Eugene and Eastern
• A little-documented railroad with an unknown name operated between the community of Scio and the Southern Pacific at a junction called West Scio by the Southern Pacific. The line was abandoned soon after 1900. It is only mentioned briefly in the The Southern Pacific in Oregon.
• The Central Pacific owned the line between Natron and Oakridge for about 10 years.

• The Oregon Trunk and the Des Chutes built a connection from Bend north to the Columbia River. After they were done, the Great Northern built a line south from Bend. However, this history is really a part of the Oregon Trunk in many regards.
• The Central Pacific was involved in a line north to Klamath Falls from California.
• The City of Prineville is one of the few remaining municipal short lines in the USA.
• The Southern Pacific built their new Natron Cutoff from Eugene to Klamath Falls over Willamette Pass, giving them access to the southern end of central Oregon, and were involved with a line to Lakeview.

• The Longview Portland and Northern - this line operated in several locations, but the longest lasting one was in the city of Gardiner, on the southern Oregon coast.
• The WCTU Railway serves an industrial area near White City, linking it to the outside world.
• The Pacific and Eastern was part of a plan to open a new line into California, but only operated a line from Medford to Butte Falls.
• The Klamath Northern operated near Chemult in order to connect a lumber mill to the outside world. It still appears on railroad maps, but does not appear to be operating under that name at this time.

• Sumpter Valley - Oregon's famous narrow gauge line of the east ran from 1891 to 1961. Track length was about 80 miles, from Baker City through Sumpter to Prairie City, where construction stopped in 1910.
• Malheur Valley operated a line from Ontario to Vale and Brogan. It was leased to the Oregon Short Line in 1907, and in 1910 became part of the OWR&N.
• Northwestern Railroad Co. started in 1906 as a short line building northwest from Huntington, OR. along the Snake River. It was sold in 1910 and 1911 ( two separate deeds ) to the OWR&N. It is not clear if the 58 miles of track to Robinette, Brownlee, Copperfield and Homestead was ever operated independently, or if the line only operated under OWR&N.
• Oregon & Northwestern started life as the Malhuer Railroad in 1923. In 1930 it was operating a 50 mile railroad all the way to Seneca and had changed names to Oregon & Northwestern. In Seneca, the line connected to the Edward Hines Lumber Co. lines running eastward. Despite the common carrier nature of the company, its primary purpose was to move lumber products for its parent, Edward Hines Lumber Co. It was abandoned in 1990.