Union Pacific Station
The most significant railroad serving Salt Lake City was Union Pacific, with its main line extending between Los Angeles, Las Vegas and Ogden. Grant Tower was a major railroad junction in Salt Lake City, and the UP station was along the east part of a wye involving UP trackage. The main lines went north to Ogden and west towards Las Vegas and Los Angeles. While the old UP Provo Subdivision was a branch line extending south.
Union Depot
The Union Depot in Salt Lake City served the Rio Grande, as well as Western Pacific. The most famous train for both of these railroads was the California Zephyr, which switched railroads here. The Rio Grande main line extended south and east to Provo and Denver, and north to Ogden. Pollard Jct., 1/2 mile north of the station, was where the WP line turned west towards San Francisco.
Salt Lake City has undergone a number of railroad relocations through its history. The Salt Lake City's Grant Tower page at the UtahRails.net web site includes further information.
Amtrak's California Zephyr basically continues to use the former Rio Grande and Western Pacific routing through Salt Lake City. All of these railroads are now part of Union Pacific. Between Salt Lake City and Smelter, 18 miles west, the old UP line towards Los Angeles and the former WP line are now operated as a double track line, the Lynndyl Subdivision. Some segments of both former railroads have been abandoned or relocated, with abandonments due to highway construction and other factors.