President Barack Obama began a second term Monday by coupling a distinctly progressive agenda for the next four years with a call for common purpose in a still-divided nation.

Sounding many of the same notes he did in the campaign, Obama launched an aggressive defense of the nation’s social welfare programs and vowed action on the contentious topics of immigration, climate change and gay rights. He punctuated calls for progress on each of those issues with the refrain “our journey is not complete.”

“Being true to our founding documents does not require us to agree on every contour of life,” Obama said. “It does not mean we all define liberty in exactly the same way or follow the same precise path to happiness. Progress does not compel us to settle centuries-long debates about the role of government for all time, but it does require us to act in our time.”

Before the 15-minute speech the nation’s first African-American president laid his hand on Dr. Martin Luther King Jr.’s personal Bible to take the oath of office on King’s holiday, in a ceremony imbued with references to the civil rights era. Later after the ceremony, at the request of the King family, the President and Chief Justice John Roberts signed the King Bible.

This year includes the 50th anniversary of the March on Washington and 150th anniversary of the Emancipation Proclamation. Former NAACP chair Myrlie Evers-Williams — whose civil rights activist husband Medgar Evers was assassinated in Mississippi in 1963 – gave an invocation that evoked that tumultuous era.

In addition, U.S. Rep. John Lewis, an Atlanta Democrat, was recognized at a Capitol luncheon with the president for having spoken across the way at the Lincoln Memorial at the March on Washington. He is the last living speaker from the event.

The civil rights battles for 84-year-old Thomas Bristow of DeKalb County predate the 1960s. He flew in the all-black Tuskegee Airmen squadron in World War Two, then flew again in Korea. Given his treatment by his government and society in those days, he never imagined witnessing the inauguration of a black president. Seated in a wheelchair just steps away from the podium on Monday, he saw it for the second time.

“To see how things have changed, not only I’m a citizen of the United States but I feel more welcome because the doors have been open now, the bars have been taken down,” he said. “… Just to see this, I just can’t hardly express myself. It’s just happy by the grace of God that I lived to see this great event.”

In his speech Obama took an unprecedented step in an inaugural in calling for the advancement of gay rights, as he connected that battle to movements of the past. Obama referenced the 1969 Stonewall riots that were a backlash to police harassment of gays in New York City, tying it to the race riots in Selma, Ala., and the Seneca Falls women’s rights convention.

Some of Obama’s most pointed words had to do with ongoing budget strife and the notion expressed by some conservatives – most notably his election foe Mitt Romney, via hidden camera – that a significant portion of the country is made up of freeloaders.

“The commitments we make to each other through Medicare and Medicaid and Social Security, these things do not sap our initiative, they strengthen us,” Obama said. “They do not make us a nation of takers; they free us to take the risks that make this country great.”

After he finished, Obama paused before walking into the Capitol, saying, “I want to take a look one more time. I’m not going to see this again.”

The crowd he saw made yet more history. An inauguration planning official told the Associated Press the crowd was estimated at more than 800,000 — by far a second-term record, though it was not nearly the size of the 1.8 million-strong crowd for his first inauguration in 2009.

Among them were thousands of Georgians who made the trip. Some wanted to be in the presence of the man they worked to re-elect, some wanted to share in like-minded strangers’ joy and some just wanted to witness history.

“Not to sound corny or anything, but it’s hope,” said Brianna Watts, a 19-year-old student at the University of Georgia. “During the speech the people around me were cheering him on, saying, ‘God bless you.’ You can’t get that from watching at home.”

Watts was standing under a large television screen on the National Mall. That’s about where Tamecia Wright, 34, of Lithonia, was in 2009. This time she vowed to get closer, so she put in her request for inauguration tickets with Georgia Republican U.S. Sen. Johnny Isakson’s office early. Nearly three years early.

Isakson, who gave out many of his 383 tickets in order of requests received, made sure Wright had a spot.

“Even though it’s the second time, I just felt like it was still a historical moment and I definitely wanted to be a part of it,” Wright said.

Many of the Obama supporters who swarmed Washington felt that the second victory validated the Obama presidency more than any policy victory, and expressed hope that more could be done in a second term after a sometimes rocky initial four years.

Elijah Staggers, a University of Georgia student who made the trip with eight of his Alpha Phi Alpha fraternity brothers, said he wanted the government to “tighten its belt” more in Obama’s second term, after it ran up record deficits in the first.

Heated conflict over the budget and gun control — which Obama hinted at with a mention of Newtown, Conn., where a gunman murdered schoolchildren last month — are sure to resume shortly in the capital, even though Congressional Republicans mostly held off their criticism in the spirit of the day. The nation’s divisions were still clear in the smattering of anti-abortion protesters and even in the inaugural program itself.

Atlanta Rev. Louie Giglio had initially been slated to give the benediction, but he quickly stepped down when an old sermon surfaced in which he preached that gays are bound for hell. He was replaced with the Rev. Luis Leon, who preaches across the street from the White House at St. John’s Church — and who made a point to offer a message of inclusiveness.