United States territorial acquisitions
The Panama Canal Zone was an unorganized US territory located within the Republic of Panama. It was established under the Hay–Bunau-Varilla Treaty in 1903 and disestablished in 1979 under the Torrijos–Carter Treaties. Panama gained full control over the Panama Canal in 1999.
Panama Canal
In 1921, Colombia and the United States entered into the Thomson–Urrutia Treaty, in which the United States agreed to pay Colombia $25 million: $5 million upon ratification, and four-$5 million annual payments, and grant Colombia special privileges in the Canal Zone. In return, Colombia recognized Panama as an independent nation.