Large swaths of the mid-Atlantic U.S. have ground to a halt as a historic storm continues to bury the region in astonishing levels of snow. Hundreds of thousands are without power, transportation systems are crippled in multiple cities, the postal service has suspended operations, and hospitals are barring their staffs from leaving until the storm is over. Washington, D.C. declared a state of emergency as a hangar roof at Dulles Airport collapsed, crushing planes and, in an extremely rare move, the normally indomitable Smithsonian closed. Accumulation totals have topped 30 inches in parts of Virginia, and the snow in not expected to let up until tonight. Forecasters believe it could break the record set by the Knickerbocker Blizzard of 1922, which dumped 28 inches on the nation's capital.