As of now, the fastest train route in the United States is Amtrak’s Acela service along the Northeast Corridor (Boston – New York – Washington, D.C.).
Here are the key details:
Important context:
While Acela is the fastest in current operation, it’s much slower than high-speed trains in Europe and Asia (which often exceed 180–200 mph). The U.S. does not yet have true “high-speed rail” by global standards, but several projects are in development (e.g., California High-Speed Rail, Brightline West from Las Vegas to Southern California).
Future:
Amtrak is working on new Avelia Liberty trainsets and Northeast Corridor infrastructure upgrades to allow sustained higher speeds and shorter trip times in the coming years.