Panama Canal
Colombia, France, and later the United States controlled the territory surrounding the canal during construction. The US continued to control the canal and surrounding Panama Canal Zone until the 1977 Torrijos–Carter Treaties provided for handover to Panama. After a period of joint American–Panamanian control, in 1999, the canal was taken over by the Panamanian government. It is now managed and operated by the government-owned Panama Canal Authority.
Panama Canal Railway
Following the United States' acquisition of Alta California in 1846 and the Oregon Territory in 1848, following the Mexican–American War and with the prospective movement of many more settlers to and from the West Coast, the United States again turned its attention to securing a safe, reliable, and speedy link between the Atlantic and Pacific oceans. In 1846 the United States signed a treaty with Colombia (then the Republic of New Granada) by which the United States guaranteed Colombian sovereignty over Panama and was authorized to build a railroad or canal at the Panamanian isthmus, guaranteeing its open transit.