BOSTON, Feb 16 (Reuters) - Record-breaking cold gripped the eastern United States while an icy winter storm crippled the nation's central states and then plowed into the mid-Atlantic, dumping snow and forcing federal offices in Washington, D.C. to close on Tuesday.

Heavy snowfall and ice moving eastward from the Southern Plains pounded Missouri, Arkansas, southern Illinois, Tennessee, Kentucky, Indiana and Ohio, the National Weather Service said.

With the storm headed east and sleet and freezing rain expected to also take a swipe at the South, states of emergency were declared in North Carolina, Virginia, Mississippi, Georgia, Kentucky, as well as in Washington, D.C.

The U.S. Office of Personnel Management announced on its web site that federal offices are closed in D.C. Fort Knox, a U.S. Army post south of Louisville, Kentucky, also will be closed on Tuesday due to weather and road conditions, it said on its website.

Airlines canceled nearly 2,600 U.S. flights, with the hardest hit airports in North Carolina and Tennessee.

Freezing rain encased Tennessee in ice, closing roads, schools and tourist attractions, including the home of the king of rock 'n' roll, Elvis Presley's Graceland mansion in Memphis.

Sleet in Arkansas shut schools and Governor Asa Hutchinson told nearly all government workers to stay home.

Cars skidded off roads near Louisville, Kentucky, where there were six times the usual number of accidents and a fleet of more than 1,000 snow plows tried to clear slick roads, officials said.

"It's been all hands on deck," said Chuck Wolfe, spokesman for the Kentucky Transportation Cabinet.

Citing nasty weather, Kentucky's state legislature said it would not reconvene until Wednesday at the earliest.

The storm dumped 10 inches (25 cm) of snow on Cincinnati and then headed east to Washington, D.C., slamming the nation's capital with heavy snow that could pile as high as 12 inches, said NWS meteorologist Brian Hurley.

"Washington and Baltimore, that's where the bull's-eye's going to be," Hurley said.

Slippery roads in western Pennsylvania on Monday were blamed for a collision between a van and a school bus carrying 13 students about 60 miles (95 km) southeast of Pittsburgh, state police said. Several people were hurt, although the extent of the injuries was unknown.

About 50 million Americans were under wind chill advisories as the mercury plunged to new depths, breaking records in New York City, where it was 5 degrees Fahrenheit (minus 15 Celsius), breaking the previous record for Feb. 16 of 9 degrees Fahrenheit in 2003, and Washington, D.C., where it was 6 degrees Fahrenheit, compared with 11 degrees Fahrenheit recorded in 1987, said Hurley.

The weather front, expected to reach Boston by Wednesday, follows a weekend storm that dumped 16 inches, making it the snowiest February in the city's history. In the scramble to clear snow on Monday before the next round arrives, one person died while shoveling in Brighton and prison inmates from the Massachusetts Department of Corrections were put to work clearing mass transit rail lines.

"The heaviest stuff will be close to the coast in eastern Massachusetts," Hurley said.

The new storm will be followed by another arctic front, bringing frigid cold to the eastern United States by Thursday or Friday, Hurley said.