Construction of the Surf Line between Los Angeles and San Diego began on October 12, 1880, with the organization of the California Southern Railroad Company.

On January 2, 1882, the California Southern commenced passenger and freight service between National City and Fallbrook Junction, just north of Oceanside.

[citation needed] For much of the 20th century, the Surf Line (officially, the Fourth District of the Los Angeles Division[5]) was to the Santa Fe what the New York City–Philadelphia corridor was to the Pennsylvania Railroad.

[9] Commuter trains began operating in the 1990s, initially as an outgrowth of existing Amtrak services until the establishment of Metrolink and Coaster by the California State Legislature in 1992.

Freight traffic includes military vehicles and equipment to Camp Pendleton and the Navy ports in San Diego.

About two-thirds of the 60-mile (97 km) segment from the Orange County line to the Santa Fe Depot in downtown San Diego has been double-tracked.

[12] A 2.6-mile (4.2 km) section of double track between Elvira (SR 52) and Morena (Balboa Avenue) was completed in July 2020.

The $192 million project, which began in August 2015, completed 14.6 miles (23.5 km) of double track from San Diego northward.

[20] In August, the California Coastal Commission had emphasized the need to move the railroad tracks inland as they reviewed the emergency permits for the stabilization work.

[22] Local leaders, including SANDAG’s executive director, showed Secretary of Transportation Pete Buttigieg the coastal erosion at the bluffs in October 2022.

[31][32] Falling debris did not damage the tracks but ground movement continued from a landslide involving Casa Romantica on the bluff above.

[35] During the work closures, freight trains are able to resume at a speed of 10 miles per hour (16 km/h) as officials were on site to clear them when it is safe to proceed.

[36][37] Orange County Transportation Authority (OCTA), which owns the section of track,[38] declared an emergency on June 12 to speed up construction of temporary barrier wall at the bottom of the slope.

[49][50] The first study, that started in August 2023, will identify the issues that impact the rail corridor, offer solutions to protect it, and develop the cost of the necessary improvements.

[51] As stated above, sections of the Surf Line in Del Mar and San Clemente will be relocated inland from their current locations to reduce the amount of times of service disruption.

The California High-Speed Rail will run on a brief portion of the Surf Line between Los Angeles and Anaheim as part of its full Phase 1 route.

For a list of stations that currently operate, see the articles for Metrolink's Orange County Line and the Coaster or the templates to the right.