The third annual “American Roots Fourth of July Concert” offers a great opportunity to sample a spectrum of U.S.-based folk and roots music styles. Rock ‘n’ roll legend Carl Perkins and San Francisco blues guitarist Joe Louis Walker top the bill: Perkins will be joined by Scotty Moore and drummer D.J. Fontana, who played with Elvis in his early rockabilly days. Sharing the spotlight are Irish-American folk stars Cherish the Ladies, leading Cajun revival outfit Beausoleil (helmed by fiddle wizard Michael Doucet), R&B veterans the Orioles, and the Puerto Rican bomba y plena of Los Pleneros de la 21. From 3-9 p.m. at the Sylvan Theater, Washington Monument Grounds. FREE. (202) 619-7226. (Ken Roseman)