The Underground Railroad:

The Underground Railroad was neither a railroad nor was it underground. It was called that because of the high secrecy it maintained and the codewords that were used like Cargo for slaves and Stations for safe houses (Eastern Illinois University). The slaves had to travel long distances without food or water with the slave catchers always on their tail. That made traveling during the day impossible. So, under the cover of darkness, they would travel ten to twenty miles house to house. The slaves were not allowed to get education, so the conductors used quilts to give directions to the passengers. For example, a quilt with a bow tie on it might mean to change clothes, or a bear paw might tell them to go through the mountains following trails of animals. To symbolize a station, people hung lanterns outside their houses. Eventually, the operation led over 100,000 people to freedom (History).