Selma is marking the 51st anniversary of the voting rights demonstration that came to be known as "Bloody Sunday."
Officials expect thousands of people to fill the west Alabama city this weekend for Selma's annual Bridge Crossing Jubilee.
The event won't be as large as last year, when President Barack Obama and others attended to mark the 50th anniversary of Bloody Sunday.
But thousands are still expected to participate Sunday as activists and others re-enact the event by walking across the Edmund Pettus Bridge.
Law enforcement officers used clubs and tear gas on marchers in Selma on March 7, 1965, as they tried to walk to Montgomery.
The attack set the stage for the Selma-to-Montgomery march, which helped build support for congressional approval of the Voting Rights Act months later.