WASHINGTON >> President Barack Obama urged Americans Sunday to draw energy and lessons of peace and patience from the Rev. Martin Luther King Jr., the slain Baptist minister honored among presidents with a memorial on the National Mall.

What Obama didn’t need to say suggested much of the progress King had sought: The nation’s first black president was dedicating the first memorial to a black man on the National Mall, a circumstance the memorial’s designers didn’t envision when they began work more than 15 years ago.

But all around the sun-splashed, star-studded event were reminders of the gap between King’s famous dreams of equality and the nation’s imperfect reality in 2011. Now, too, the nation remains riven by war, economic crisis and, in some quarters, distrust of government.

"I know we will overcome," Obama, who was 6 when King was assassinated in 1968, proclaimed to the crowd of several thousand.

"He had faith in us," the president added. "And that is why he belongs on this Mall: because he saw what we might become."

The memorial’s dedication has special meaning for the Obamas. The president credits King for opening his way to the White House and makes reference to the civil rights leader in many speeches. Two nights earlier, the first family opted for a more private visit to the site — before the crowds and the cameras arrived.

In the glare of bright sun and television lights Sunday, King’s daughter Bernice, his son Martin Luther King III and Harry Johnson Sr., president and CEO of the Martin Luther King Jr. Memorial Project Foundation, gave the first family a second tour. The group walked along the memorial’s long inscription wall and stopped at a large silver box — a time capsule to be buried at the memorial. Obama’s daughters, Sasha and Malia, each dropped a scroll inside. A White House aide confirmed that they were signed copies of the president’s inaugural speech and his address to the 2008 Democratic National Convention.

They moved on to the granite monument: two jagged boulders representing the "mountain of despair" King described, with a massive "stone of hope" removed from the middle and pushed ahead. Carved from the central piece is the 30-foot sculpture of King, arms crossed, staring out over the reflecting pool and past the Jefferson Memorial to the horizon.

"Are you all happy with it?" the president asked the King family. Bernice King replied yes.

In his speech, Obama did not directly mention himself or name any specific dynamics dividing the nation. But he focused on King’s broad themes — equality, justice and peaceful resistance — and served up a reminder that "the hardships we face are nothing compared to those Dr. King and his fellow marchers faced 50 years ago."

But in one section, the way Obama described King’s struggles drew clear parallels with his own.

"Even after rising to prominence, even after winning the Nobel Peace Prize, Dr. King was vilified by many," Obama, a Nobel Prize winner himself, said.

"He was even attacked by his own people, by those who felt he was going too fast of those who felt he was going too slow," the president said. Obama has taken criticism from the right for the signature health care overhaul and from the left — the Congressional Black Caucus and progressives in the Democratic party — for compromising too easily with Republicans on fiscal issues.

Obama then pivoted to the nation’s political polarization, the distrust of institutions and the acidic tone of debate.

"If he were alive today, I believe he would remind us that the unemployed worker can rightly challenge the excesses of Wall Street without demonizing all who work there," Obama told the crowd, in comments that seemed aimed at the protests against the wealthy and powerful, from Wall Street to Washington and beyond.

Obama seemed to address the tea partiers and others who have scored major political victories with searing demands that government shrink itself and stop spending so much taxpayer money.

"He would want us to know we can argue fiercely about the proper size and role of government without questioning each other’s love for this country," Obama said, "with the knowledge that in this democracy, government is no distant object but is rather an expression of our common commitments to one another."

Americans could learn something about the tone of debate from King, too, Obama said.

"He would call on us to assume the best in each other rather than the worst, and challenge one another in ways that ultimately heal rather than wound."