Barack Obama has become the 44th president of the United States.

Obama was sworn into the nation's highest office at an inaugural ceremony held at 11 a.m. Tuesday ET at the west front of the U.S. Capitol. He is the fourth-youngest president in U.S. history at 47 and the first African American to assume the office. Former Delaware Senator Joe Biden also assumed his new post of vice presidency.

Obama took the presidential oath of office in front of a crowd that stretched for kilometers at the National Mall in the U.S. capital and overwhelmed its public transportation system.

The official swearing-in ceremony featured an invocation by the Reverend Rick Warren, pastor of Saddleback Church and author of The Purpose Driven Life.

Following Obama's inaugural address, writer Elizabeth Alexander read a poem.

An inaugural lunch for the new president followed the speech. The Inaugural Parade passed from the Capitol to the White House.