Complex sentence: On January 20,2009, Obama was inaugurated as the 44th president of the United States in a ceremony viewed by nearly 2 million people, the largest congregation of spectators ever to witness the inauguration of a new president.
Split into simpler sentences: On January 20,2009, Obama was inaugurated as the 44th president of the United States. The ceremony was viewed by a crowd of around 2 million people and was the largest congregation of spectators to ever be present for an inauguration of a new president.