The Southern Pacific was an American Class I railroad network that existed from 1865 to 1996 and operated largely in the Western United States. The system was operated by various companies under the names Southern Pacific Railroad, Southern Pacific Company and Southern Pacific Transportation Company.

Union Pacific Corporation is a publicly traded railroad holding company. It was incorporated in Utah in 1969 and is headquartered in Omaha, Nebraska. It is the parent company of the current, Delaware-registered, form of the Union Pacific Railroad, and the company, along with Berkshire Hathaway-owned rival BNSF, has a near-duopoly on freight railroad transportation west of the Mississippi River.