The impeachment trial of President Andrew Johnson took place in 1868 after he faced several articles of impeachment, with the primary charge being his violation of the Tenure of Office Act. This act was designed to limit the president's power to remove certain officeholders without the Senate's approval. Johnson's dismissal of Edwin M. Stanton, the Secretary of War, prompted his impeachment by the House of Representatives. The trial was held in the Senate, where a two-thirds majority was required for conviction, which would lead to his removal from office.

The trial began in March and lasted several weeks, capturing the attention of the nation. The debate centered not only on the legality of Johnson's actions but also on broader questions about presidential authority and the power dynamics following the Civil War. The Republican-controlled Senate, which largely opposed Johnson's lenient policies toward the Southern states, seemed poised to remove him. Ultimately, when the vote was cast on May 26, he was acquitted by just one vote, with the final tally being 35 for conviction and 19 against.

This narrow acquittal marked a significant moment in the balance of power between the presidency and Congress and reflected the lingering divisions from the war. Johnson's presidency continued, though his influence was severely weakened. This event also set a procedural precedent regarding the impeachment process in the United States, specifically concerning the required thresholds for removal from office. The ramifications of this acquittal lasted for decades, influencing how impeachment would be viewed and carried out in the future.