In addition to preserving historic sites associated with the Underground Railroad, the NPS, through the Network to Freedom, attempts to tell a comprehensive story of the people and events associated with the struggle for freedom from enslavement. Much of the historic physical evidence of places—the buildings and landscapes—important to the Underground Railroad have been altered or destroyed. To convey the magnitude of this history, it is necessary to recognize commemorative and interpretive efforts, in addition to identifying and preserving the sites that remain. Consequently, the Network was designed to include not only sites, but facilities and programs.
By law, the Network includes the following categories or "elements":
All units and programs of the National Park Service determined by the Secretary of Interior to pertain to the Underground Railroad.
Other Federal, State, local, and privately owned properties pertaining to the Underground Railroad that have a verifiable connection to the Underground Railroad and that are included on, or determined by the Secretary to be eligible for inclusion on, the National Register of Historic Places.
Other governmental and non-governmental facilities and programs of an educational, research, or interpretive nature that are directly related to the Underground Railroad.
The last category, "governmental and non-governmental facilities and programs" is much more flexible and invites the inclusion of a variety of different categories of listings. Facilities and programs in the Network can have an educational, research, or interpretive scope, as long as they are directly related to, and verifiably associated with, the Underground Railroad. Facilities can include, but not be limited to, archives and libraries, research centers, museums and museum collections, and cultural or commemorative centers. Programs can be even more diverse in nature. They can include, but not be limited to, tours, interpretive talks, travelling exhibits, theater productions, living history presentations, and educational programs.
Finally, there are a multitude of Underground Railroad-related sites around the United States that have suffered the impacts of prolonged negligence or developments inconsistent with the historical character of the site. For whatever reasons, these past activities may have left the site ineligible for the National Register of Historic Places. Nonetheless, these sites are often integral parts of the Underground Railroad story. Their significance should not be lost, so the Network to Freedom is designed to include these impacted sites, with the provision that they must be associated with some type of documentation and interpretation.