Midway Atoll is a 2.4 sq mi (6.2 km2) atoll in the North Pacific Ocean. Midway Atoll is an insular area of the United States and is an unorganized and unincorporated territory. The largest island is Sand Island, which has housing and an airstrip. Immediately to the east of Sand Island across the narrow Brooks Channel is Eastern Island, which is uninhabited and no longer has any facilities. Forming a rough, incomplete circle around the two main islands and creating Midway Lagoon is Spit Island, a narrow reef.

In the law of the United States, an insular area is a U.S.-associated jurisdiction that is not part of a U.S. state or the District of Columbia. This includes fourteen U.S. territories administered under U.S. sovereignty, as well as three sovereign states each with a Compact of Free Association with the United States. The term also may be used to refer to the previous status of the Swan Islands, Hawaii, Puerto Rico, and the Philippines, as well as the Trust Territory of the Pacific Islands when it existed.