Andrew Johnson (December 29, 1808 – July 31, 1875) was the 17th President of the United States, serving from 1865 to 1869.Johnson became president as he was vice president at the time of President Abraham Lincoln's assassination.A Democrat who ran with Lincoln on the National Union ticket, Johnson came to office as the Civil War concluded.egotiated by the United States Minister to Britain, former Maryland senator Reverdy Johnson, in late 1868, it was ignored by the Senate during the remainder of the President's term. The treaty was rejected after he left office, and the Grant administration later negotiated considerably better terms from Britain.