南太平洋鐵路
The Union Pacific Corporation merged the third Union Pacific Railroad into the Southern Pacific Transportation Company in 1998; the Southern Pacific Transportation Company becomes the surviving railroad and at the same time the Union Pacific Corporation renamed the Southern Pacific Transportation Company to fourth incarnation of the Union Pacific Railroad. The former Southern Pacific Transportation Company is now operating as the current incarnation of the Union Pacific Railroad. The Southern Pacific Rail Corporation remained a subsidiary of the Union Pacific Corporation until 2015 when it was merged into the former Southern Pacific Transportation Company, the current Union Pacific Railroad.