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.ndrew Johnson (December 29, 1808 – July 31, 1875) was the 17th President of the United States, serving from 1865 to 1869.