The primary charge against Johnson was a violation of the Tenure of Office Act
Why Was Andrew Johnson Impeached?
Andrew Johnson was the 17th president of the United States who served from April 15, 1865 to May 5, 1869. He was impeached on February 24, 1868, after violating the Tenure of Office Act. Johnson had fired Edwin M. Stanton, the Secretary of War, which was in violation of the law that requires the president to get Senate approval before dismissing a member of the cabinet.
Edwin M. Stanton was a radical and an influential Republican, and the Republican members of the House of Representatives sought to impeach the Democrat president three days later. Johnson had fired Stanton because of the constant clashes with members of the Republican Party concerning the treatment of the South after the end of the American Civil War. Republicans considered the president sympathetic and friendly to former slaveholders. Although the Republicans had more than the required two-thirds membership in the Senate, a small number of those members chose to support the president’s action, and Johnson ultimately survived the conviction by a single vote.