How didn't the US get access to the Canal Zone in panama?

An initial attempt by France to build a sea-level canal failed after a great amount of excavation was carried out. This was of use to the United States, which completed the present Panama Canal in 1913 and officially opened it in 1914.
Along the way, the State of Panama was created through its separation from Colombia in 1903, due to a US backed revolt, so the US could then get control of the Canal project area.
After construction, the canal and the Canal Zone surrounding it were administered by the United States.
On September 1977, U.S. President Jimmy Carter signed the Torrijos-Carter Treaty, which set in motion the process of handing over the canal to Panamanian control.
The treaty provided for a twenty-year period during which Panama would have increasing responsibilities for Canal operations, culminating in complete U.S. withdrawal in 12/1999.
The Canal Zone is now run by the Panama Canal Authority.