BNSF Harbor Subdivision

The Harbor Subdivision is a historic single-track main line of the BNSF Railway which stretches 26 miles (42 km) between rail yards near downtown Los Angeles and the ports of Los Angeles and Long Beach across southwestern Los Angeles County. It was the primary link between two of the world's busiest harbors and the transcontinental rail network. Mostly displaced with the April 15, 2002 opening of the more direct Alameda Corridor, the Harbor Sub takes a far more circuitous route from origin to destination, owing to its growth in segments over the decades. The subdivision was built in this fashion beginning in the early 1880s to serve the ports and the various businesses that developed along it.

First built to serve Port Ballona and Santa Monica, located at what is now Playa del Rey, the construction of a larger, better port at Redondo Beach brought an extension to that city in 1888. The early 1900s would see that project eclipsed with the coming of the San Pedro Outer Breakwater and the Port of Los Angeles. By the early 1920s, owing to the development of the area's oil fields, the Harbor Sub was extended through Torrance, Wilmington and on to Long Beach. Development of Watson Yard in Wilmington completed the line. Other than sidings at "Lairport" (along the eastern edge of Los Angeles International Airport next to Aviation Boulevard at 120th Street), "Ironsides" in Torrance and the line's longest siding at the Alcoa, also in Torrance, the Harbor Sub is completely single-track without signals, compensated with track warrant control via a local dispatcher.

...
Wikipedia