The Social Democratic League of America (SDL) was a short-lived American political party established in 1917 by electorally-oriented socialists who favored the participation of the United States in World War I. Led by such intellectuals as John Spargo, Emanuel Haldeman-Julius, and William English Walling, the SDL maintained effective control over the venerable socialist newspaper The Appeal to Reason (then known as The New Appeal) during 1918, the year of the group's greatest public influence.