Mississippi is a state with a legacy of poverty, injustice and, subsequently, great blues music. Which is what you'd expect from a group called the North Mississippi Allstars. The jam band specializes in blues and rock sounds and has been thrice-nominated for Grammy awards. It's also served as the backing band for John Hiatt. Its latest release, "Hernando," is more of the deep South swamp blues that's an important export of the Magnolia State. Lead singer Luther Dickinson has been tapped to tour with the Black Crowes this year; but before that happens, he'll be with his brother and drummer, Dicky, at the National Saturday, May 17, at 9 p.m., keeping the blues alive. Alvin Youngblood Hart opens. $17.50. 612-1900 or visit www.thenationalva.com.