Due to Lincoln being associated with freeing the slaves, the Memorial has been a center for civil rights protests in the United States. In 1939, Marian Anderson sang there because she could not sing at Constitution Hall. The Memorial has been used many times for famous events. Martin Luther King's "I Have a Dream" speech was given on the steps of the Lincoln Memorial. President Richard Nixon once met with protesters of the Vietnam War, who were at the Memorial. A concert was given for President Barack Obama at the Memorial before he took office.