Obama Ceremonially Sworn-In for Second Term

Much symbolism attached to event's occurrence on Martin Luther King day

President Barack Obama thanked supporters Sunday as he urged Americans to come together to take action that will pay tribute to the nation's history and its future.

"All of you here understood and were committed to the basic notion that when we put our shoulders to the wheel of history, it moves. It moves forward," he said at a reception at the National Building Museum, his final public event before Monday's inaugural festivities.