Crowds streamed into the nation’s capital Tuesday, jamming subway cars and packing the National Mall from the Capitol to the Washington Monument hours before President-elect Barack Obama was to be sworn in.

For weeks, officials urged people to arrive early for the historic inauguration of the nation’s first black president and throngs of revelers heeded that advice, streaming onto the Mall hours before daybreak.

By 7 a.m., some 207,000 people had entered Washington’s Metro transit system, officials said. Huge lines formed outside subway stations; many parking lots filled up and had to be closed.

“Platforms are extremely crowded,” Metro spokeswoman Lisa Farbstein said. Lines were six to 10 deep at fare machines.

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Meanwhile, thousands of people gathered near the parade route on Pennsylvania Avenue, occasionally erupting in spontaneous cheers and chants of “open the gates!” The large crowds made it difficult for many to figure out where checkpoints into the secure area were.

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Police have projected crowds ranging between 1 and 2 million for the inauguration. It’s possible that attendance could top the 1.2 million people who were at Lyndon Johnson’s 1965 inauguration, which is the largest crowd the National Park Service has on record.

In 1981, President Ronald Reagan’s inauguration drew about 500,000 people, and President Bill Clinton’s 1993 inauguration drew about 800,000 people, according to park service estimates.

Crowd counting has long been a controversial issue. The National Park Service says Congress ordered it to stop doing crowd counts in 1997 after the agency was accused of underestimating numbers for the 1995 Million Man March.

Thousands of charter buses from across the country were in the District of Columbia, packing parking lots and even streets that closed Monday night to accommodate the surge of overnight visitors and day-trippers.

On the closing list Tuesday are all inbound bridges connecting D.C. and Virginia, though authorized vehicles, pedestrians and bicyclists are allowed. A sizable chunk of downtown Washington will be shut down, and other sections will not permit parking. The two subway stations near the National Mall will be closed for much of the day.