Note to OPB - ALL Amtrak trains have arrived / departed King St. Station since May 1, 1971. The last remaining train to use Seattle Union Station, A UP " Pool Service " roundtrip from Portland, OR., was abolished on that date. The Milwaukee Road, which also used Union Station, discontinued its last passenger train, the Olympian Hiawatha, in 1961. The Right Of Way leading to Union Station is now a busway North of Spokane St.; concrete bases from Milwaukee's electrification are still in place between the double track South of Spokane St.
As noted by Sasquatch, Seattle's 2 train stations are on the South side of Jackson St., separated by 4th Ave. South. Both stations have " 2nd Floor " entrances @ the North elevated street level. At one time there was a connecting track under the 4th Ave. viaduct for express & mail interchange.( The old Post Office was adjacent to King St. Station. ) Sadly, although the renovated Union Station is quite a sight to see, a new office building is located on top of the platform & depot trackage area.