Crowds streamed into the nation’s capital Tuesday, packing mass transit before dawn as out-of-towners and area residents alike headed for Pennsylvania Avenue and the National Mall for the swearing in of President-elect Barack Obama.

"This is the culmination of two years of work," said Obama activist Akin Salawu, 34, of Brooklyn, N.Y., who helped the candidate as a community organizer and Web producer. "We got on board when Obama was the little engine who could. He’s like a child you’ve held onto. Now he’s going out into the world."

By 4 a.m. EST Tuesday, lines of riders formed in suburban parking lots for the Metro transit system, which put on extra trains for the expected rush.

Trains were crowded, and riders seemed to be in a jubilant mood, despite the early hour. World history teacher Calvin Adams of Arlington, Va., said he got up extra early so he could witness history being made first-hand and teach it to his classes.

"Eventually I’ll teach American history," said Adams, 23. "I’ll say, ‘This is how it works because I’ve been there, I’ve seen it.’"

Washington’s Metrorail subway line opened at 4 a.m., an hour earlier than usual, to bring the huge crowds into the city.

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.

At the District’s L’enfant plaza Metro station about 1,000 riders — many of them evidently new to the city’s subway system — waited to exit and were having trouble getting through the unfamiliar turnstiles. And, there was standing room only on some suburban Virginia lined. Maryland transit authorities reported that parking lots in several suburban Metro subway stations were filled at 6 a.m. And on the state’s highways, there was moderate to heavy traffic.

By 4:15 a.m., a line of cars extending at least one-and-a-half miles formed on the far right lane Interstate 66 in Virginia. The travelers were driving eastbound and trying to land a coveted parking spot at the Vienna metro. While parking spots were still plentiful, drivers were forced to travel single-file to enter the station’s parking garages.

"We’re prepared; we’re braced," said Steven Taubenkibel, spokesman for the District’s Metro mass-transit system.

City and local planners have consistently warned visitors that they could expect extensive transportation delays.

On the closing list Tuesday are all inbound bridges connecting the District of Columbia 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.

For those hoping to taxi in or out of town, be warned. Some taxi drivers have decided not to work the full day — because of the closings and because they also wanted a chance to watch the inauguration.

Taxi driver Ephrem Zewdie, a native of Ethiopia, planned to work only Tuesday morning. Then, he would drive home to suburban Maryland, ride a subway train into the city and join the crowds on the Mall.

"I was following the election from the beginning," Zewdie said. "Even though I’m not a citizen, I’m very excited."

D.C. police have projected inaugural crowds between 1 million and 2 million. Planners say attendance could easily top the 1.2 million people who were at Lyndon B. Johnson’s 1965 inauguration, the largest crowd the National Park Service has on record.

Such crowds means visitors must be extra diligent in keeping track of their belongings — and each other — in near-freezing temperatures.

At Union Station on Monday, social studies teacher Ashley Weaver kept an eye on her 24 students, who sat on the floor eating lunch. They arrived Saturday from Eagle Valley High School in Gypsum, Colo.

"I took students four years ago to the inauguration, and it was nothing like this," said Weaver, 27. "There’s a huge mass of people."


Associated Press Writers Gillian Gaynair, Alan Fram, Ricardo Alonso-Zaldivar and Kevin Freking contributed to this report.