Zoomable Google Maps show the most interesting locations throughout the country where Amtrak trains switch between different lines, along with Amtrak routings serving various old Union Stations.

New London CT
Amtrak's Montrealer briefly diverged here from the Northeast Corridor main line.

Albany NY
An interruption of service east to Boston, and the removal of a segment of track considered unneeded at the time, necessitated some creative detouring with a backup move for a few years.

Entering Quebec
At one time, two different Amtrak trains operated into Montreal, operating into two different stations.

The introduction of the Capitol Limited involving two different railroads, required construction of a new connecting track east of the station.

New Castle PA
The switch of the Broadway Limited to the Baltimore & Ohio route west of Pittsburgh, resulted in a new connecting track from the former Pennsylvania Railroad.