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.
Separation of Panama from Colombia
In 1903, the United States and Colombia signed the Hay–Herrán Treaty to finalize the construction of the Panama Canal but the process was not completed because the Congress of Colombia rejected the measure (which the Colombian government had proposed) on August 12, 1903. The United States then moved to support the separatist movement in Panama to gain control over the remnants of the French attempt at building a canal.