Depended on celestial navigation

the Underground Railroad, the South/North escape routes used by freedom-seeking slaves during the 19th century.
Slaves traveling the Underground Railroad, usually on foot, depended on celestial navigation to find their way northward. They continually looked to the Big Dipper and the North Star for direction.
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NASA CORE - Videotape/Underground Railroad: Connections to Freedom and Science
http://catalog.core.nasa.gov/core.nsf/item/008.0-10V