Stepping into history, Barack Hussein Obama grasped the reins of power as America's first black president on Tuesday, saying the nation must choose "hope over fear, unity of purpose over conflict and discord" to overcome the worst economic crisis since the Great Depression.

In frigid temperatures, an exuberant crowd of more than a million packed the National Mall and parade route to celebrate Obama's inauguration in a high-noon ceremony. They filled the National Mall, stretching from the inaugural platform at the U.S. Capitol to the Lincoln Memorial in the distance.