I grew up near what is now called Gap Cave (formerly Cudjo’s Cave) in Cumberland Gap, Tennessee. (Sidenote: if you’re ever in that area, the National Park Rangers give a fantastic 2 hour guided tour). It was said that Gap Cave was used in Civil War times as a hospital. Caves being a natural choice when choosing shelter, these tips on how to construct a half-cave shelter come from “Shelters, Shacks, and Shanties” by D.C. Beard, 1914.