It is presently the northern terminus of the Caltrain commuter rail line serving the San Francisco Peninsula and Santa Clara Valley.

4th & King is one block from Oracle Park, the home ballpark of the San Francisco Giants of Major League Baseball.

[5] The Portal project (formerly the Downtown Rail Extension) to the rebuilt Salesforce Transit Center includes the construction of an underground 4th and King station.

The underground portion will be adjacent to the current station on the Townsend Street side,[6] but Caltrain will continue using the surface platforms.

[7] Until that time, California High-Speed Rail trains are planned to utilize the existing station with modifications for that service.