Editor's note: Following earlier unconfirmed reports that officials had canceled today's anniversary march across Selma's Edmund Pettus Bridge due to crowd size, people have begun traversing the span, with thousands more queued up behind them. However, a pastor at the scene has suggested to NBC News that the number of people massed at the bridge may interfere with plans for special guests to participate. - Tricia
Editor's note: We are following reports that Alabama officials have halted today's symbolic march over the Edmund Pettus Bridge in Selma, Ala., due to the large number of participants, and will update when details are given. - Tricia
Selma is a city in and the county seat of Dallas County, in the Black Belt region of lower west Alabama. Located on the banks of the Alabama River, it has a population of 20,756 as of the 2010 census. The city is best known for the 1965 Selma Voting Rights Movement and the Selma to Montgomery marches that originated in the city.