This Day in History: Selma to Montgomery March Begins

March 21, 1965. Led by Dr. Martin Luther King Jr., between 3,000 and 8,000 marchers crossed the Edmund Pettus Bridge out of Selma on their way to Montgomery. Over the next five days, they were protected by thousands of federalized Alabama National Guardsmen and soldiers. Their numbers would swell to around 25,000. At the state capitol, King would give his famous "How Long, Not Long" speech.