The Panama Canal is an artificial 82 km (51 mi) waterway in Panama that connects the Atlantic Ocean with the Pacific Ocean. The canal cuts across the Isthmus of Panama and is a conduit for maritime trade. Canal locks are at each end to lift ships up to Gatun Lake, an artificial lake created to reduce the amount of excavation work required for the canal, 26 m (85 ft) above sea level, and then lower the ships at the other end. The original locks are 34 m (110 ft) wide.
France began work on the canal in 1881, but stopped due to engineering problems and a high worker mortality rate. The United States took over the project in 1904 and opened the canal on August 15, 1914. One of the largest and most difficult engineering projects ever undertaken, the Panama Canal shortcut greatly reduced the time for ships to travel between the Atlantic and Pacific oceans, enabling them to avoid the lengthy, hazardous Cape Horn route around the southernmost tip of South America via the Drake Passage or Strait of Magellan.
Colombia, France, and later the United States controlled the territory surrounding the canal during construction. 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 SS Ancon.
By the 1930s, water supply became an issue for the canal, prompting the construction of the Madden Dam across the Chagres River above Gatun Lake. Completed in 1935, the dam created Madden Lake (later Alajeula Lake), which provides additional water storage for the canal. In 1939, construction began on a further major improvement: a new set of locks large enough to carry the larger warships that the United States was building at the time and planned to continue building. The work proceeded for several years, and significant excavation was carried out on the new approach channels, but the project was cancelled after World War II.
After World War II, US control of the canal and the Canal Zone surrounding it became contentious; relations between Panama and the United States became increasingly tense. Many Panamanians felt that the Canal Zone rightfully belonged to Panama; student protests were met by the fencing-in of the zone and an increased military presence there. Demands for the United States to hand over the canal to Panama increased after the Suez Crisis in 1956, when the United States used financial and diplomatic pressure to force France and the UK to abandon their attempt to retake control of the Suez Canal, previously nationalized by the Nasser regime in Egypt. Panamanian unrest culminated in riots on Martyr’s Day, January 9, 1964, when about 20 Panamanians and 3–5 US soldiers were killed.
A decade later, in 1974, negotiations toward a settlement began and resulted in the Torrijos–Carter Treaties. On September 7, 1977, the treaty was signed by President of the United States Jimmy Carter and Omar Torrijos, de facto leader of Panama. This mobilized the process of granting the Panamanians free control of the canal so long as Panama signed a treaty guaranteeing the permanent neutrality of the canal. The treaty led to full Panamanian control effective at noon on December 31, 1999, and the Panama Canal Authority (ACP) assumed command of the waterway. The Panama Canal remains one of the chief revenue sources for Panama today.