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
The construction of the canal was completed in 1914, 401 years after Panama was first crossed by Vasco Núñez de Balboa. The United States spent almost $500,000,000 (roughly equivalent to $9,169,650,000 now) to finish the project. This was by far the largest American engineering project to date. The canal was formally opened on August 15, 1914, with the passage of the cargo ship .