The private working land base of America's forests is being converted to developed uses, with implications for the condition and management of affected private forests and the watersheds in which they occur. The Forests on the Edge project seeks to improve understanding of the processes and thresholds associated with increases in housing density in private forests and likely effects on the contributions of those forests to timber, wildlife, and water resources. This report, the first in a series, displays and describes housing density projections on private forests, by watershed, across the conterminous United States. An interdisciplinary team used geographic information system (GIS) techniques to identify fourth-level watersheds containing private forests that are projected to experience increased housing density by 2030. Results indicate that some 44.2 million acres (over 11 percent) of private forests--particularly in the East, where most private forests occur--are likely to see dramatic increases in housing development in the next three decades, with consequent impacts on ecological, economic, and social services. Although conversion of forest land to other uses over time is inevitable, local jurisdictions and states can target efforts to prevent or reduce conversion of the most valuable forest lands to keep private working forests resilient and productive.