Who was the first U.S. President to be impeached?

Andrew Johnson was the first U.S. President to be impeached in 1868. His impeachment arose primarily from his violation of the Tenure of Office Act, which restricted the President's power to remove certain officeholders without the Senate's approval. This act was largely viewed as a means to limit Johnson's authority, especially in the context of the post-Civil War Reconstruction era. The impeachment process in the House of Representatives culminated in a trial in the Senate, where Johnson was ultimately acquitted by a single vote.

The significance of Johnson's impeachment lies not only in its historical context but also in its implications for the balance of power among the branches of government, as it set a precedent for future impeachments. While other presidents such as Bill Clinton and Richard Nixon faced impeachment proceedings, Johnson remains the first. The attempt to impeach Clinton in the late 1990s and Nixon’s resignation in the face of impending impeachment in the early 1970s reflect ongoing tensions in presidential power and accountability, but they occurred after Johnson's historical precedent.