Known as the world's automotive center, "Detroit" is a metonym for that industry. Detroit's auto industry, some of which was converted to wartime defense production, was an important element of the American "Arsenal of Democracy" supporting the Allied powers during World War II. It is an important source of popular music legacies celebrated by the city's two familiar nicknames, the Motor City and Motown. Other nicknames arose in the 20th century, including City of Champions, beginning in the 1930s for its successes in individual and team sport; The D; Hockeytown (a trademark owned by the city's NHL club, the Red Wings); Rock City (after the Kiss song "Detroit Rock City"); and The 313 (its telephone area code).