The Central Pacific Railroad began building the San Joaquin Valley Line south from Lathrop just 24 months after completing the western portion of the 1869 Transcontinental Railroad. The San Joaquin Valley Line was built to connect Northern and Southern California. It exits the south end of the Valley through Tehachapi Pass and continues on through the desert to Los Angeles. The Line opened the San Joaquin Valley to settlement, and became part of the Southern Pacific (SP) Railroad in 1875. SP was incorporated into the Rio Grande-Southern Pacific Railroad in 1988, and RGSP was purchased by the Union Pacific Railroad (UP) in 1996. The Valley Line is now a busy part of the UP system.