Harriet Tubman was the most famous leader of the "Underground Railroad." (Photo: Library of Congress)

By the early 1800's, most Northern states had taken steps to end, or abolish, slavery. During the mid-1800s, abolitionists began to enter politics and use their homes to help black slaves escape the South to enjoy freedom in the North. This was called the "Underground Railroad" even though it wasn't underground and didn't involve any trains. Hiding places were known as "stations" and people who helped were called "conductors." Harriet Tubman, a runaway slave herself, was one of the most famous conductors, helping about 300 blacks escape to freedom.

President Lincoln and his Cabinet review the Emancipation Proclamation. (Illustration: North Wind Picture Archives)

Abolitionists won their biggest victory when President Abraham Lincoln issued the Emancipation Proclamation on January 1, 1863. This famous proclamation declared the slaves free in many parts of the South. In 1865, the 13th Amendment to the U.S. Constitution abolished slavery entirely.