How did slaves travel north to freedom?

Slaves traveled north to freedom by using the Underground Railroad with little or no food, no protection and they had to travel very long distances to reach their destination.

They used the Underground Railroad System and followed the North Star

Explanation:

The Underground Railroad was a network of secret routes and safe houses established in the United States during the early to mid-19th century, and used by enslaved African-Americans to escape into free states and Canada. The scheme was assisted by abolitionists and others sympathetic to the cause of the escapees.

The North Star was of course towards the North so that is how Slaves were able to know which way to travel.