Greenbacks, which were backed by neither silver nor gold but by the credit of the United States, and which were necessitated by vast wartime expenditures, had helped to finance the war.[12] In the late 1860s, politicians disagreed about how quickly to have the government resume paying out gold and silver in payment of its obligations. Treasury Secretary Hugh McCulloch felt the best way to return to that practice was to withdraw the greenbacks as quickly as possible, and he did so until stopped by Congress, which felt his contractionist stand was hurting the economy.[13] More and more silver was being mined in the Far West.