An estimated 7 million acres of U.S. land has been undermined. Already, approximately 1.9 million of those acres have been affected by surface subsidence. Of the 100,000 underground coal mines that exist, 90,000 are presently abandoned or inactive, leaving nearly 5.2 million acres of undermined area that has not yet subsided. Of that figure, about 500,000 acres are situated under urban, populated areas. This article discusses the insurance implications of this situation.