PHILADELPHIA (AP) _ President-elect Barack Obama, tracing the train route Abraham Lincoln took nearly a century and a half earlier, undertook the final leg of his inaugural journey to the U.S. capital Saturday, pledging to reclaim America’s spirit but also warning of steep challenges facing the country.

Hundreds of excited people cheered as Obama waved from the back of the train when it rolled slowly through the station in little Claymont, Delaware, on the way to larger crowds at stops in Wilmington and Baltimore on the route to Washington.

Unfazed by frigid temperatures, scattered onlookers stood waving at crossroads along the way.

“Starting now, let’s take up in our own lives the work of perfecting our union,” Obama told several hundred people gathered inside a hall at Philadelphia’s historic 30th Street train station before embarking for Washington where he will be inaugurated Tuesday as the first African-American U.S. president.

“Let’s build a government that is responsible to the people and accept our own responsibilities as citizens to hold our government accountable. … Let’s make sure this election is not the end of what we do to change America, but the beginning and the hope for the future.”

While talking about the future, Obama reflected on the past, echoing the words of the Declaration of Independence, Lincoln and President John F. Kennedy. He cited the founding fathers who risked everything with no assurance of success in Philadelphia in the summer of 1776 when they declared independence from the British king:

“They were willing to put all they were and all they had on the line _ their lives, their fortunes and their sacred honor _ for a set of ideals that continue to light the world: That we are equal. That our rights to life, liberty, and the pursuit of happiness come not from our laws, but from our maker. And that a government of, by, and for the people can endure.”

It’s a momentous time for the Obamas. And for Michelle Obama, it was also her 45th birthday.

The president-elect’s triumphant day _ to be heralded by cheering throngs along the 137-mile (220-kilometer) rail route _ started in Philadelphia with a sober discussion of the country’s future with 41 people he met during his long quest for the White House.

At the outset, he told a crowd gathered in a flag-draped room that the same perseverance and idealism displayed by the nation’s founders are needed to tackle the difficulties of today.

“We recognize that such enormous challenges will not be solved quickly,” Obama said. “There will be false starts and setbacks, frustrations and disappointments. And we will be called to show patience even as we act with fierce urgency.”

He cited the faltering economy, the wars in Iraq and Afghanistan _ “one that needs to be ended responsibly, one that needs to be waged wisely” _ the threat of global warming and U.S. dependence on foreign oil.

“We are here today not simply to pay tribute to our first patriots but to take up the work that they began,” he said. “The trials we face are very different now, but severe in their own right. Only a handful of times in our history has a generation been confronted with challenges so vast.”

Preparing to board the train, Obama said that “what’s required is a new declaration of independence _ from ideology and small thinking.”

Obama’s vintage rail car was tacked onto the back of a 10-car train made up of Amtrak passenger train cars filled with hundreds of guests, reporters and staff along for the ride.

As the train pulled out of the station at Philadelphia, the conductor said: “Welcome aboard the 2009 inaugural train to D.C.”

Obama traveled from Philadelphia to Wilmington, Delaware, where he was welcomed at the station by Vice President-elect Joe Biden and his wife, Jill, before a rally outside the train station. Then Obama was giving a speech in Baltimore before his arrival at Washington’s Union Station after nightfall.

At Union Station, as Obama set out from Philadelphia, the vanguard of perhaps the greatest crowd in Washington history was beginning to arrive.

Bursting with enthusiasm, Toni Mateo arrived from Atlanta, where he works at a public relations firm.

“It’s going to be life-affirming for me,” said Mateo. “It was really important that I come here to represent the family and to take the energy back with me.” He said his train car was crowded but quiet _ until “I just screamed out `Obama,’ and the whole crowd erupted.”

Obama’s train was also to make a “slow roll” through the town of Edgewood, Maryland, so more people could see Obama waving from the rear platform. Curious onlookers also were expected to gather on overpasses, parking lots and commuter train stations hoping to get a glimpse of the president-elect.

Obama was to deliver a speech before as many as 100,000 at Baltimore’s War Memorial Plaza. Pressing the inaugural theme of service and community, event planners also called for drives to collect canned food for the needy in Wilmington and Baltimore to coincide with his stops.

Temperatures were in the single digits Fahrenheit (teens Celsius) in Philadelphia, but the energy in the room warmed the crowd.

“Hello Philadelphia!” Obama shouted to cheers.

Back in Washington, members of his administration stayed focused on policy.

Addressing the winter meeting of the U.S. Conference of Mayors, Valerie Jarrett, a senior Obama adviser, asked for help keeping the momentum going for passage, and implementation, of a measure to jump-start the economy.

House Democrats this week unveiled their version of the bill, an $825 billion package of tax cuts and spending.

Although his path tracked Lincoln’s and took on the same overtone of high security, it wasn’t the journey of virtual secrecy that the 16th president-elect took so long ago on the eve of the Civil War that would result in the abolishment of slavery. Lincoln was smuggled under cover of darkness from one train station to another to avoid a feared assassination attempt.

Meanwhile, plans were going ahead for an outdoor inauguration despite cold weather forecasts for next week. Temperatures are expected to be in the 30s (about 0 Celsius).

Somewhere between 1 million and 2 million people are expected to make their way to Washington for the swearing in ceremony and inaugural parade. Some 240,000 tickets have been issued for the festivities at the Capitol, with 28,000 seats.

The FBI has been planning its inauguration mission since June. Large trucks, a bomb-detecting robot, canisters with hundreds of gallons of water to disrupt a car bomb and other emergency response equipment stretch down a block near the FBI’s Washington Field Office.

John Perren, a special agent in charge of counterterrorism, said there was no credible intelligence warning of any attack.

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Associated Press Writers Jennifer Loven on the Obama train, Darlene Superville, Nafeesa Syeed and Eileen Sullivan in Washington contributed to this report.