Southern Pacific Transportation Company
The Union Pacific Corporation was established the same year the current Union Pacific railroad began. The current Union Pacific Railroad is the fourth incarnation and it is referred to as Mark II; the current incarnation of the Union Pacific Railroad is formerly known as the Southern Pacific Transportation Company, the last incarnation of the Southern Pacific railroad. The Union Pacific Corporation merged the third Union Pacific Railroad into the Southern Pacific Transportation Company and then renamed the Southern Pacific Transportation Company to the current Union Pacific Railroad.