What significant even showed the conflict that existed between President Andrew Johnson and Congress?

The significant event that highlighted the conflict between President Andrew Johnson and Congress was his impeachment in 1868. Johnson's violation of the Tenure of Office Act by attempting to remove Edwin M. Stanton, the Secretary of War, without Senate approval led Congress to take action against him. This confrontation epitomized the struggle over Reconstruction policies and the balance of power between the presidency and Congress. Ultimately, Johnson was acquitted by one vote, but the conflict underscored the deep divisions in post-Civil War America.