The Guam National Wildlife Refuge is composed of three units: the Andersen Air Force Base Overlay Unit, the Navy Overlay Unit, and the Ritidian Unit. The Ritidian Unit, known to the native CHamoru people as Puntan Litekyan, is located on the northern tip of Guam and encompasses approximately 1,217 acres, including 385 terrestrial acres and 832 acres of submerged areas offshore.

Guam is an organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, and the most populous village is Dededo. It is the westernmost point and territory of the United States, reckoned from the geographic center of the U.S. In Oceania, Guam is the largest and southernmost of the Mariana Islands and the largest island in Micronesia.