Andrew Johnson built his political career in Tennessee while operating a tailoring business. He served in local government and the state legislature before entering the United States House of Representatives in 1843. During ten years in Congress he advocated inexpensive land for settlers and presented himself as a defender of white working people against wealthy interests. As Tennessee governor from 1853 to 1857 he supported education and public improvements; election to the Senate followed in 1857.

Although a slaveholder and Democrat, Johnson rejected secession. He remained in the Senate when Tennessee left the Union in 1861, making him the only senator from a seceding state to retain his seat. Abraham Lincoln appointed him military governor of Tennessee in 1862. He worked to restore Union authority under wartime conditions and eventually endorsed emancipation.

Johnson became president after Lincoln's assassination in April 1865. His Reconstruction program offered pardons and permitted southern states to restore governments with limited federal requirements. Former Confederate leaders regained influence, and new state governments enacted Black Codes restricting freed people's rights. Johnson opposed broad federal protection of African American citizenship and insisted that Reconstruction largely belonged to the executive branch and the returning states.

His vetoes of the Freedmen's Bureau legislation and the Civil Rights Act of 1866 deepened conflict with Congress. Republicans overrode the civil rights veto, and the Fourteenth Amendment and Reconstruction Acts moved policy away from his approach. His public campaign against congressional opponents failed in the 1866 elections.

The House impeached Johnson in February 1868 after he attempted to remove Secretary of War Edwin Stanton under disputed legal authority. The Senate fell one vote short of the two-thirds majority required to convict, leaving him in office but with sharply reduced political authority. His administration also included the 1867 purchase of Alaska, negotiated by Secretary of State William Seward, and pressure supporting French withdrawal from Mexico. After leaving the presidency in 1869, Johnson unsuccessfully sought other offices before winning election to the Senate in 1875. He died that July. His career illustrates the distinction between preserving the Union and defending equal citizenship: his resistance to Black civil rights severely obstructed the settlement of emancipation.