Why was president Andrew Johnson impeached?

Answer 1

Wasn't he the one that put a cigar up a girls butt in the oval office and then denied doing it?
One of them did but I forgot which one.

Answer 2

There were two contending theories in post-war Washington concerning reconstruction. One theory argued that the states of the United States are indestructible by the acts of their own people and state sovereignty cannot be forfeited to the national government. Under this theory, the only task for the federal government was to suppress the insurrection, replace its leaders, and provide an opportunity for free government to re-emerge. Rehabilitation of the state was a job for the state itself. The other theory of reconstruction argued that the Civil War was a struggle between two governments, and that the southern territory was conquered land, without internal borders-- much less places with a right to statehood. Under this theory, the federal government might rule this territory as it pleases, admitting places as states under whatever rules it might prescribe.

Andrew Johnson was a proponent of the first, more lenient theory, while the radical Republicans who would so nearly remove him from office were advocates of the second theory. The most radical of the radical Republicans, men like Thaddeus Stevens and Charles Sumner, believed also in the full political equality of the freed slaves. They believed that black men must be given equal rights to vote, hold office, own land, and enter into contracts, and until southern states made such promises in their laws they had no right to claim membership in the Union. (Republicans also had more practical reasons to worry about Johnson's lenient reconstruction policy: the congressmen elected by white southerners were certain to be overwhelmingly Democrats, reducing if not eliminating the Republican majorities in both houses.)

Answer 3

For violating the Tenure of Office Act. This Act set forth the argument about Presidential appointments that, having required the advise and consent of the Senate to be effective, that same body should also advise and consent to anyone the President wanted to dismiss from office.
That particular Act of Congress was later ruled to be repugnant to the Constitution and therefore null and void in a decision handed down by the Supreme Court many years later.