President Woodrow Wilson pressed a telegraph key in the White House on October 10, 1913 and set off charges two thousand miles away that blew the Gamboa dike, letting the water of Gatun Lake into the Culebra Cut. From that moment a ship could pass from the Atlantic to the Pacific without leaving the water. The canal had taken 33 years in total, more than 5,600 lives in the American phase and an estimated 22,000 in the French one, and it had another ten months of finishing before traffic was allowed through.
The French tried first. Ferdinand de Lesseps, who had dug Suez, began in 1881 on a sea-level canal with no locks, which was the wrong design for the isthmus, and the company went bankrupt in 1889 with its equipment rusting in the jungle and its workforce dead of yellow fever and malaria. The Americans took over in 1904. They changed the design to a lock canal with an artificial lake. Before they could dig anything they had to deal with the disease: William Gorgas drained the standing water, fumigated the houses and screened the barracks, and yellow fever was gone from the zone by 1906.
The rest was earth moving. Nobody had attempted it on that scale. The Culebra Cut ran nine miles. It went through the continental divide, and the spoil taken out of it was used to build the Gatun dam, fill valleys and ballast the railway that ran alongside the excavation, roughly 160 million cubic yards of it in the seven years George Washington Goethals was in charge. The locks lift ships 85 feet in three steps and drop them the same way, and every transit uses one lockful of fresh water taken from the lake, which is why a dry year is a problem for the canal.
The first full transit, the ship Ancon, came on August 15, 1914. It was done. Panama took the waterway over on December 31, 1999 under the treaties signed by Torrijos and Carter in 1977, and a third lane of larger locks opened in 2016. Around 14,000 ships now use it in a year.