Transport networks were preparing to shut down and residents were warned they could be forced to spend up to five days indoors. The forecast was for 2.5 feet (0.76 metres) of snow to fall, and for blizzard conditions.
Heavy snowfall has already been blamed for hundreds of accidents and the deaths of a father and son who were trying to help a crashed motorist in Virginia.
A huge area of the eastern seaboard was affected. Virginia, Maryland, and the District of Columbia each declared "snow emergencies", allowing them to call in assistance from the National Guard.
Several thousand residents lost electricity in West Virginia and more power cuts were expected.
The predicted snowfall is the biggest in the region for ninety years.
The National Weather Service warned that conditions would be "extremely dangerous," with heavy, wet snow and strong winds. They warned that transport would be affected and supplies to shops could be delayed.
Airlines cancelled flights, schools closed and the federal government sent workers home, where they could be stuck for several days in a region ill-equipped to deal with so much snow. Some hospitals asked people with four-wheel-drive vehicles to volunteer to pick up doctors and nurses to take them to work.
The National Zoo closed early and the Smithsonian museums planned to close on Saturday. Flights on Saturday afternoon were cancelled at Dulles International Airport in suburban Washington. Amtrak stopped most trains heading south from Washington, affecting fans heading to the Super Bowl in Miami.
Before the heavy snow started falling, shoppers jammed aisles and emptied stores of milk, bread and shovels.
In western Virginia, a tractor-trailer struck and killed a father and son who had stopped to help another driver who had crashed in snow on Interstate 81, Virginia State Police said. William Edward Smith Jr., 25, and 54-year-old William Edward Smith Sr. died at the scene, authorities said.
The storm comes less than two months after a storm on December 19th dumped more than 16 inches of snow on Washington.
