* Preserving the Union: Johnson's most significant accomplishment was preventing the Southern states from seceding from the Union and preserving the United States as a single nation. He did this by refusing to recognize the legitimacy of the Confederate government and by sending federal troops to enforce the Union's authority in the South.
* Reconstruction: Johnson also oversaw the Reconstruction of the South after the Civil War. He did this by appointing provisional governors for the Southern states and by establishing the Freedmen's Bureau to help former slaves adjust to their new lives as free men.
* Civil Rights: Johnson was also a strong advocate for civil rights for African Americans. He supported the passage of the Civil Rights Act of 1866, which granted African Americans citizenship and the right to own property, and the 14th Amendment to the Constitution, which guaranteed African Americans equal protection under the law.
* Vetoes: Johnson was also known for his use of the veto power. He vetoed more bills than any other president up until that time, and many of his vetoes were overridden by Congress. This led to a great deal of conflict between Johnson and Congress.
* Impeachment: Johnson was also the first president to be impeached by the House of Representatives. He was impeached for "high crimes and misdemeanors," but he was acquitted by the Senate.
Johnson's presidency was a tumultuous time in American history, but he did manage to accomplish a great deal. He preserved the Union, oversaw the Reconstruction of the South, and advocated for civil rights for African Americans.