Complex sentence: From 1986 to 1999 it was Salt Lake City's Amtrak station, replacing Salt Lake City Union Pacific Depot, served by the "California Zephyr", "Desert Wind", and "Pioneer", the latter two discontinued in 1997.
Split into simpler sentences: From 1986 to 1999 the depot served as Salt Lake City's Amtrak station, replacing the Union Pacific Depot. It was served by the "California Zephyr", "Desert Wind", and "Pioneer" trains, with the latter two having been discontinued in 1997.