The Panama Canal Zone was a 553 square miles (1,432.3 km²) unorganized U.S. territory

Insular area

An insular area is a United States territory, that is neither a part of one of the fifty U.S. states nor the District of Columbia, the federal district of the United States...

 located within the Republic of Panama, consisting of the Panama Canal

Panama Canal

The Panama Canal is a ship canal in Panama that joins the Atlantic Ocean and the Pacific Ocean and is a key conduit for international maritime trade. Built from 1904 to 1914, the canal has seen annual traffic rise from about 1,000 ships early on to 14,702 vessels measuring a total of 309.6...

 and an area generally extending 5 miles (8.1 km) on each side of the centerline, but excluding Panama City

Panama City

Panama is the capital and largest city of the Republic of Panama. It has a population of 880,691, with a total metro population of 1,272,672, and it is located at the Pacific entrance of the Panama Canal, in the province of the same name. The city is the political and administrative center of the...

 and Colón

Colón, Panama

Colón is a sea port on the Caribbean Sea coast of Panama. The city lies near the Atlantic entrance to the Panama Canal. It is capital of Panama's Colón Province and has traditionally been known as Panama's second city....

, which otherwise would have been partly within the limits of the Canal Zone. Its border spanned two of Panama's provinces and was created on November 18, 1903 with the signing of the Hay-Bunau Varilla Treaty

Hay-Bunau Varilla Treaty

The Hay–Bunau-Varilla Treaty was a treaty signed on November 18, 1903, by the United States and Panama, that established the Panama Canal Zone and the subsequent construction of the Panama Canal...

.