The Reconstruction Act of 1867 divided the Southern states into military districts headed by Union generals. It required the states to grant voting rights to African American men and ratify the 14th Amendment in order to be readmitted to the Union. Johnson vetoed the act but Congress overrode his veto. This set up a conflict between Johnson and the Radical Republicans that led to his impeachment for violating the Tenure of Office Act, though he was acquitted by one vote in the Senate trial. The election of 1868 was won by Ulysses S. Grant, signaling Republican control over Reconstruction.