In addition to Lincoln and Twain many other famous writers and activists spoke at Plymouth, including William Lloyd Garrison, Wendell Phillips, Charles Sumner, John Greenleaf Whittier, Clara Barton, Charles Dickens, Ralph Waldo Emerson, Horace Greeley, and William Thackery. More recently, in February 1963, Martin Luther King Jr. preached a sermon on "The American Dream," echoed just months later in his famous "I Have a Dream" speech at the Lincoln Memorial in Washington, DC. Senator Hillary Clinton spoke at Plymouth in 2001, and two noted minimalist composers, Philip Glass and Charlemagne Palestine, gave concerts using Plymouth's Aeolian-Skinner organ.