This map is a derivative work of a map layer from nationalatlas.gov, which states: "We have begun by collaboratively building "frameworks," the essential map layers that provide a foundation for all other maps. These basic layers, including small-scale harmonized information on North American roads, water, boundaries and the like, are being offered here for the first time. Like all other raw data and documentation offered here on nationalatlas.gov, these frameworks can be downloaded at no cost and used freely without copyright concerns or license restrictions."[1]