What is Amtrak?

Legal Definition
The National Railroad Passenger Corporation, doing business as Amtrak /ˈæmtræk/, is a passenger railroad service that provides medium- and long-distance intercity service in the contiguous United States. Founded in 1971 to take over most of the remaining U.S. passenger rail services, it is partially government funded yet operated and managed as a for-profit corporation.

Amtrak serves more than 500 destinations in 46 states and three Canadian provinces, operating more than 300 trains each day over 21,300 miles (34,000 km) of track. Some track sections allow trains to run as fast as 150 mph (240 km/h). In fiscal year 2015, Amtrak served 30.8 million passengers and had $2.185 billion in revenue, while employing more than 20,000 people. Nearly two-thirds of passengers come from the 10 largest metropolitan areas; 83% of passengers travel on routes shorter than 400 miles (644 km). Its headquarters is at Union Station in Washington, D.C.

The name "Amtrak" is a portmanteau of the words "America" and "trak", the latter itself a sensational spelling of "track".
-- Wikipedia
Legal Definition
A train service started in 1971 that is operated by the national railroad passenger corporation. It was needed after a decline in passenger train services. Its regulated by the government. It is in 48 states.