He joined and quit several political parties in the furtherance of the progressive causes in which he believed. After serving in the Union Army in the American Civil War, Weaver returned to Iowa and worked for the election of Republican candidates. After several unsuccessful attempts at Republican nominations to various offices, and growing dissatisfied with the conservative wing of the party, in 1877 Weaver switched to the Greenback Party, which supported increasing the money supply and regulating big business.