During the March on Washington 50 years ago today, Martin Luther King Jr. called to “let freedom ring” from the mountains and hilltops of every state. And in honor of the anniversary on Wednesday, bells will ring at more than 100 locations across the country. President Obama will join former presidents Bill Clinton and Jimmy Carter to ring a bell that hung at the 16th St. Baptist Church in Birmingham, Alabama, before the deadly bombing there in 1963. Some of the sites that will ring bells are symbolic—such as the Topeka, Kansas, monument to the landmark 1954 ruling Brown v. Board of Education. International ceremonies will be held in London’s Trafalgar Square as well as in Japan, Switzerland, Nepal, and Liberia.