High Quality Content by WIKIPEDIA articles! The Western Pacific Railroad (reporting mark WP) was a Class I railroad in the United States. It is now part of the Union Pacific Railroad (UP). It was the second railroad company to use this name. The original Western Pacific Railroad (1862-1870) was established in 1865 to build the western-most portion of the Transcontinental Railroad between San Jose, California (later Oakland, California), and Sacramento, California. This company was absorbed into the Central Pacific Railroad in 1870.