The idea of a shortcut
Before the canal, a ship sailing between the Atlantic and Pacific coasts of the Americas had to go around Cape Horn at the southern tip of South America, a long and often dangerous passage. The narrow isthmus of Panama offered an obvious shortcut. Spanish colonial traffic had long crossed it by land, and in the mid-19th century the California Gold Rush made a rapid crossing valuable, leading to a railway across the isthmus, opened in 1855.
A canal would cut thousands of miles from voyages between, say, New York and San Francisco, and open new options for trade between Europe and the west coast of the Americas.
The French attempt
The French company headed by Ferdinand de Lesseps, who had led the Suez Canal project, began work in 1881. De Lesseps favoured a sea-level canal like Suez, but Panama’s terrain, heavy rainfall and the Chagres River made the task far harder. Landslides, financial mismanagement and above all disease took a heavy toll. Yellow fever and malaria killed a very large number of workers, and the company collapsed at the end of the 1880s, with a scandal in France following. The effort left excavations and equipment, but no working canal.
The American construction
The United States took up the project in the early 1900s after the Panama revolt of 1903, when Panama separated from Colombia, and signed a treaty giving the United States rights over a canal zone. Work began in 1904.
Several decisions proved crucial. Public-health measures, led by the physician William Gorgas, targeted the mosquitoes that carry yellow fever and malaria, through drainage, screening and fumigation, and these greatly reduced the death rate. The engineer John Stevens organised the railway and excavation on a workable basis, and George Goethals, an army engineer, oversaw the project to completion. The plan was changed from a sea-level canal to a lock canal, which raised ships to an artificial lake, Gatun Lake, created by damming the Chagres River.
The labour force was international, with large numbers of workers from the Caribbean, particularly Barbados, as well as from Europe. The work was dangerous, and many thousands of workers died across the French and American periods. The canal opened to traffic on 15 August 1914, a time when the outbreak of the First World War overshadowed the event.
How a transit works
A ship entering from the Atlantic passes through the Gatun locks, a flight of three chambers that lifts it to the level of Gatun Lake. It then crosses the lake and the Culebra Cut, a deep channel dug through the continental divide, and descends to the Pacific through the Pedro Miguel and Miraflores locks. The canal is around 80 kilometres (50 miles) long. In the original locks, small electric locomotives running on tracks beside the chambers helped to hold and guide ships.
A full passage typically takes many hours, and ships book their slots in advance. The details of operation are better described by the canal authority than by a history, but the general principle, that ships are raised and lowered by gravity-fed water from the lake, is straightforward. The same principle is explained in the general history of ship canal locks.
The Panamax limit
The original lock chambers were about 33.5 metres (110 feet) wide and 305 metres (1,000 feet) long. Ships had to fit within those dimensions, with some margin. The result was the “Panamax” size, a term for the largest vessels able to pass: a beam of about 32 metres, a length that fits the chambers and a draft limited by the depth of water. Many bulk carriers, tankers and container ships were designed to just fit, because passage through the canal could save a long voyage.
Some ships were too large to use the canal at all. Large aircraft carriers and the biggest tankers and bulk ships had to go around Cape Horn or use other routes. The Panamax design influenced the shape of the world fleet for much of the 20th century, in the same way that the Suez Canal shipping route influenced tankers and cargo vessels.
Passing to Panama and expanding
The United States operated the canal for most of the 20th century, and control passed to Panama under treaties signed in 1977, with the handover completed on 31 December 1999. The canal is now run by a Panamanian authority.
As ships grew, a new, wider set of locks was built in a major expansion project, and opened in June 2016. The new chambers are much larger, about 55 metres (180 feet) wide and over 400 metres long, and permit what are called neo-Panamax ships. These can carry far more containers than the old Panamax limit allowed, and their arrival changed how shipping lines plan routes between Asia and the east coast of the United States. The older locks remain in use.
Importance
The canal remains a major route for container shipping, grain, liquefied gas and cars, linking the Caribbean sea lanes to the Pacific. Water supply in Gatun Lake, which depends on rainfall, is a continuing constraint, and periods of drought have at times limited the number and draft of ships allowed through. Its history shows how an engineering structure can set the measurements that ship designers work to for generations.