It may be handy to make a list of hotels that are either physically attached to the Amtrak station or are literally across the street. Here's a start -
Denver, Colorado Union Station -The Crawford Hotel. - Attached to the station.
Indianapolis, Indiana. - Crowne Plaza Hotel. - Sidewalk Underpass from the hotel entrance to the station entrance.
Memphis, Tennessee - The Central Station - Attached to the station.
Jackson, Mississipi - Hilton Garden Inn - Directly Across the street from the station.
Newark, New Jersey - Doubletree - Attached to the station via a covered walkway.
Kansas City, Missouri - The Westin at Crown Center - Attached to the station via a covered walkway.
Dallas, Texas - Courtyard by Mariott & La Qunita Inn - Directly Across the street from the station.
San Antonio, Texas - Staybridge Suites - Directly Across the street from the station.
Tucson, Arizona - Hotel Congress - Directly Across the street from the station.
Emeryville, California - Hyatt House Emeryville - Pedestrian Bridge over tracks connects hotel parking lot with train station.
Sacramento, California - Vagabond Inn - Directly Across the street from the station.