Hundreds of people are expected to join in when the town celebrates its 375th anniversary on Saturday, Sept. 21, on the town common from noon to 6 p.m. The community event will feature family activities including Civil War stories, fife and drum music, and more, topped by a 4 p.m. performance by the The B. Street Bombers band. There will also be vendor booths featuring art, crafts, and food. Along with the celebration, a slide presentation on the history of Salisbury Beach will be offered free at 11 a.m. and 1 p.m. at the nearby Salisbury Historical Society, on Elm Street, as part of the regional Sails and Trails event sponsored by the Essex National Heritage Area. Those interested in renting a booth may call 375th Committee co-chairwoman Maria Miles at 978-239-4246, or e-mail her at firstname.lastname@example.org. “Three hundred seventy-five years of seaside history, that’s what Salisbury’s all about,”Miles said.