Public Domain, condition of not being privately owned. The term public domain refers to public lands, uncopyrighted publications, and products not protected by a patent. The works of William Shakespeare, for example, are in the public domain since no one possesses exclusive ownership rights to them.

In the United States, public domain is most often used to designate lands owned by the federal government that are not being employed for some specific purpose, such as for a military installation. The land was acquired beginning when the original states ceded western land claims to the federal government. It was greatly increased by the addition of the Louisiana Purchase from France, Florida from Spain, and Alaska from Russia, as well as by the treaty cessions from Mexico following the Mexican War (1846-1848). Unowned land in new states became part of the public domain except in Texas, which kept control of its unowned land. Much of the land that the United States acquired was turned over to settlers by the Homestead Act of 1862 (see Homestead Laws) and similar legislation, or was granted to railroads and land-grant colleges.