Why was President Johnson was nearly impeached?
He violated the Tenure of Office Act
Impeachment of President Johnson is one of the most emblematic event that occurred during the Reconstruction. Johnson was a Democrat who opposed equality with African Americans. Johnson removed of office Edgar Stanton who had been Lincoln's secretary of state during the Civil War. It was a violation of a Tenure of Office Act. This act originally aimed at protecting him.
This was the first impeachment in US History and one of the only three that took place (Nixon and Clinton were the two other ones). Just like Clinton, Johnson was acquitted of all charges following a Senate trial.