The network used to help slaves escape was not literally underground or a railroad. It was figuratively "underground" because it was basically an underground resistance and secretive. It was known as a "railroad" due to the use of rail terminology like conductors. The Underground Railroad had meeting points, secret routes, transportation, safe houses, and personal assistance provided by abolitionist sympathizers. People who were a part of the Underground Railroad generally organized in small, independent groups since this helped maintain secrecy. Individuals knew some connecting "stations" along the route but knew all the details.
Escaped slaves would move north along the route from one station to the next. "Conductors" on the railroad came from many different backgrounds, including free-born blacks, white abolitionists, former slaves, and Native Americans. Religious communities often helped, especially the Religious Society of Friends (aka Quakers), Congregationalists, Reformed Presbyterians, and several larger groups like branches of the Methodist church and American Baptists. Without the support of free blacks, there would have been almost no chance for slaves to escape.
Escaped slaves would move north along the route from one station to the next. "Conductors" on the railroad came from many different backgrounds, including free-born blacks, white abolitionists, former slaves, and Native Americans. Religious communities often helped, especially the Religious Society of Friends (aka Quakers), Congregationalists, Reformed Presbyterians, and several larger groups like branches of the Methodist church and American Baptists. Without the support of free blacks, there would have been almost no chance for slaves to escape.
A painting by Charles T. Webber showing how free men and women helped slaves escape from their terrible conditions