On the surface they look very different--rugged northern New England with its primarily White population, the arid Lower Rio Grande Valley inhabited mainly by Hispanics, the green and humid Mississippi Delta with a mix of Black and White residents. But when it comes to economics, they have much in common--fortune passed them by.

Along with other predominantly rural regions, these areas have fallen behind the rest of the United States in many ways, from job opportunity and education to health care and living conditions. In Forgotten Places, Thomas Lyson and William Falk have brought...