Louisiana blues is a genre of blues music that developed in the period after World War II in the state of Louisiana. It is generally divided into two major subgenres, with the jazz-influenced New Orleans blues based on the musical traditions of that city and the slower tempo swamp blues incorporating influences from zydeco and Cajun music from around Baton Rouge. Major artists in the New Orleans tradition include Professor Longhair and Guitar Slim and for swamp blues Slim Harpo and Lightnin' Slim. Both genres peaked in popularity in the 1960s and were covered by a number of rock artists. Interest declined in the later 1960s but there have been occasional revivals since the 1970s.