ALLEN G. BREEDNEW YORK (AP) â¿¿ From Washington to Boston, big cities and small towns were buttoned up Monday against the onslaught of a superstorm that threatened 50 million people in the most heavily populated corridor in the nation, with forecasters warning that the New York area could get the worst of it â¿¿ an 11-foot wall of water. "The time for preparing and talking is about over," Federal Emergency Management Administrator Craig Fugate said Sunday as Hurricane Sandy made its way up the Atlantic on a collision course with two other weather systems that could turn it into one of the most fearsome storms on record in the U.S. "People need to be acting now." Forecasters said the hurricane could blow ashore Monday night or early Tuesday along the New Jersey coast, then cut across into Pennsylvania and travel up through New York State on Wednesday. Airlines canceled more than 7,200 flights and Amtrak began suspending train service across the Northeast. New York, Philadelphia, Washington and Baltimore moved to shut down their subways, buses and trains and said schools would be closed on Monday. Boston also called off school. And all non-essential government offices closed in the nation's capital. The New York Stock Exchange said it will be shut down Monday, including electronic trading. Nasdaq is shutting the Nasdaq Stock Market and other U.S. exchanges and markets it owns, although its exchanges outside the U.S. will operate as scheduled. As rain from the leading edges of the monster hurricane began to fall over the Northeast, hundreds of thousands of people from Maryland to Connecticut were ordered to evacuate low-lying coastal areas, including 375,000 in lower Manhattan and other parts of New York City, 50,000 in Delaware and 30,000 in Atlantic City, N.J., where the city's 12 casinos were forced to shut down for only the fourth time ever.