Answer:
the House of Representatives voted to impeach him.
Step-by-step explanation:
After Lincoln was assassinator, Andrew Johnson was chosen to replace him as the president.
At that point in time, the central government had to put their troops in southern states to make sure that they're following the federal's government order to treat African American people as legal citizens.
But, Andrew Johnson seems to have strong supporters from the confederates and tried to pull the troops out.
Secretary of War Edwin Stanton openly challenge Andrew Johnson decision to do this. Since he became a hindrance for Johnson, He decided to dismiss Stanton from his position.
The house of representatives saw this as an abuse of power and voted to impeach Andrew Johnson from his position as the president.