<item>1. Includes that part of drainage basin of Red River of the North, south of 49th parallel, sometimes considered part of Louisiana Purchase.
<item>2. Ceded by Spain in 1898, ratified in 1899, became Commonwealth of Puerto Rico by Act of Congress July 25, 1952.
<item>3. Acquired 1898; ratified 1899.
<item>4. Acquired 1899; ratified 1900.
<item>5. Land area only.
<item>6. Comprises the following islands (gross area in square miles): Midway, 2; Wake, 3; Palmyra, 4; Navassa, 2; Baker, Howland, and Jarvis combined area, 3; Johnston Atolls combined area, less than .5; and Kingman Reef, less than .5. Excludes Canton and Enderbury Islands combined area, 27 sq. mi. or 73 sq. km., (under jurisdiction of Kirbati since 1979); and Swan Islands, 1 sq. mi. (returned to Honduras in 1972).