Stockton, California was the location where the main lines of the Southern Pacific, Western Pacific and Santa Fe all crossed at grade, all within several blocks of each other in the downtown area. The ATSF ran east-west, while the SP and WP ran north-south. The WP and SP ran parallel through the city, although those two lines crossed on a diamond at El Pinal on the north edge of downtown.
The Union Pacific acquired the WP in 1982, and later the SP in 1996. At some point after 1996, UP abandoned the former WP line from the ex-SP diamond to a point south of the former ATSF diamond. The former WP-SP diamond is now a junction. Some rails in between the former diamonds are still in use for car storage and interchange with local shortline Stockton Terminal & Eastern. The abandoned segment passes by the former WP passenger station (still standing).
Mike Palmer adds: I visited Stockton in 1982, a couple months before the WP disappeared into the UP. The pictures enclosed here are a mixture of those from 1982, and a recent Amtrak journey through the area.
Spur to Port of Stockton: A short spur line once offered access the Port of Stockton, served by the Western Pacific Railroad. It branched from the WP mainline at a location named "North Channel", and served the port. It was abandoned under Union Pacific's control.