The National Map CorpsTNMCorps is an online crowdsourcing mapping project with volunteers successfully editing structures in all 50 States, Puerto Rico, and the U.S. Virgin Islands. As part of The National Map, structures include schools, hospitals, post offices, police stations, cemeteries, and other important public buildings. By updating and verifying structures data, volunteers are making significant contributions to USGS National Structures Database, The National Map, and ultimately U.S. Topo Maps!