The deal for 28 new passenger trains will boost Amtrak's speed and capacity along its most heavily used and profitable route, which carries more than 3.5 million passengers a year, from 2021.
The trains will carry more than 400 passengers, about one-third more than the existing Acela north-eastern corridor express service, with a maximum speed of 300 kilometres per hour, although normal speeds will be about 260 kilometres an hour.
Alstom agreed to make most of the new equipment for what will be known as Amtrak's Avelia Liberty line, at its plant in Hornell, New York.
Area home to one in seven US citizens
The trains will also serve Baltimore, Philidelphia and other cities on the 730-kilometre route and will be faster than the currently used trains partly thanks to Alstom's Tiltronix system allowing the trains to lean more deeply into curves, avoiding sharp slowdowns.
"This area from Boston to Washington is home to one out of every seven Americans," said US Vice-President Joe Biden, a strong advocate of high-speed rail.
The north-east corridor is "fundamentally important" to the US economy, he said.
Alstom's senior vice-president for North America, Jerome Wallut, called the new trains the "most advanced, reliable and safest" in the world.