Radical Republicans: A group within the Republican Party during Reconstruction that advocated for harsher measures against Southern states and greater protection for freed slaves.
Impeachment: The process of charging a public official with misconduct while in office. President Johnson became the first U.S. president to be impeached by Congress in 1868 but was not removed from office.
Tenure of Office Act: An act that limited the president's power by requiring Senate approval for removing certain government officials from their positions. Its violation led to President Johnson's impeachment proceedings.