[3] The route turned north until it crossed Overland Avenue, continued on a right-of-way between Exposition and Olympic before reaching Colorado and paralleling that road to Santa Monica.

[4] The line was built in 1875 as the steam-powered Los Angeles and Independence Railroad, intended to bring mined ore to ships in Santa Monica harbor's Long Wharf and as a passenger excursion train to the beach.

[13] With sparse population along much of the route, service on the Air Line was reduced as early as 1924, with passenger cars running only during rush hours.

Pacific Electric would reduce the Air Line's service frequency until 1931 when only a single daily round-trip operated over the route.

[15][9] By then, Pacific Electric did not print regular timetables for the Air Line, attempting to reduce ridership to strengthen their case for abandonment.

As the use of rail for transporting freight gradually declined, the tracks along Santa Monica and Sepulveda boulevards were removed and service became sparse.

The tracks alongside Exposition Park occasionally also served a special purpose to hold circus trains throughout the 1980s and to store various companies' passenger cars during the 1984 Olympic Games.

By the mid-1990s parking lots, storage facilities and some retail buildings had almost completely covered the tracks west of Sepulveda Boulevard — with unused signal cantilevers and crossing gates being the only clue to its former existence.

[21] Track replacement and various construction tasks began in 2006, and the first phase of the "Expo Line" from downtown Los Angeles to Culver City opened in April 2012.

[26] As a remnant of Southern Pacific's former steam line, the segment from Santa Monica to Port Los Angeles ran a regular local service.