Attempts to build a canal across Nicaragua to connect the Atlantic Ocean and the Pacific Ocean stretch back to the early colonial era. Construction of such a shipping route—using the San Juan River as an access route to Lake Nicaragua—was first proposed then. Napoleon III wrote an article about its feasibility in the middle of the 19th century. The United States abandoned plans to construct a waterway in Nicaragua in the early 20th century after it purchased the French interests in the Panama Canal, which has served as the main connecting route across Central America since its completion.

Because the steady increase in global shipping may eventually make the project economically feasible, speculation on a new shipping route has continued. In June 2013, Nicaragua's National Assembly approved a bill to grant a 50-year concession to the HK Nicaragua Canal Development Investment (HKND) to manage the Nicaraguan Canal and Development Project to build the canal, but little development took place, and the concession to HKND was cancelled in May 2024.Nicaragua cancels a controversial Chinese inter-oceanic canal concession after nearly a decade Los Angeles Times 8 May 2024. Retrieved 13 May 2024

Route Several possible routes for the construction of the Nicaragua Canal have been proposed, all of them using Lake Nicaragua. The following six routes have been discussed to carry traffic from the Caribbean Sea to Lake Nicaragua, which is at an elevation of above sea level:

Route 1 runs from a point near Kukra Hill on the Caribbean coast of the South Caribbean Coast Autonomous Region (RACCS) to the Escondido River and from there to Lake Nicaragua. Route 2 goes from a point near Roca Caiman on the Caribbean coast of RACCS to the Escondido River and from there to Lake Nicaragua. Route 3 runs from the city of Bluefields on the Caribbean coast of RACCS to the Bluefields River and from there to Lake Nicaragua. Routes 4 and 5 go from a point near Punta Gorda River on the Caribbean coast of RACCS to Lake Nicaragua. Route 6 runs from the town of San Juan de Nicaragua via the San Juan River to Lake Nicaragua, which is the route of the older proposal, the Ecocanal.

All the above proposed routes run from a port at or near Bluefields in the Caribbean Sea to Morrito, a small town located on the eastern shore of Lake Nicaragua. From Morrito, ships would continue westward across Lake Nicaragua to a port near the city of La Virgen in the Department of Rivas. At that point, ships would enter a manmade canal and navigate 18–24 kilometers across the isthmus of Rivas to reach the Pacific Ocean via the Brito River.

Early plans (1551–1909)

The idea of constructing a manmade waterway through Central America is old. The routes suggested usually ran across Nicaragua, Panama, or the Isthmus of Tehuantepec in Mexico. The colonial administration of New Spain conducted preliminary surveys as early as 1551, under the supervision of a Spanish explorer named Gormara. Nothing came of this initial attempt, but the idea was revived in 1781 by the Spanish Crown, and surveys were made again, this time under the supervision of an officer named Galisteo. Construction did not occur, as the crown was unable to secure adequate funding."Nicaragua Canal Project is 304 years old" Hamilton Spectator, April 25, 1891, p 3

In 1825, the newly established Federal Republic of Central America (FRCA) considered the waterway. That year, the FRCA government authorities hired surveyors to chart the route and, afterward, contacted the Federal government of the United States to seek financing and the engineering technology needed for building the shipping route, to the advantage of both nations. A survey from the 1830s stated that the waterway would be in length and would generally follow the San Juan River from the Caribbean Sea to Lake Nicaragua, then go through a series of locks and tunnels from the lake to the Pacific Ocean.

While officials in Washington, D.C. thought the project had merit, and Secretary of State Henry Clay formally presented it to the Congress of the United States in 1826, the plan was not approved. The United States was particularly concerned with Nicaragua's relatively high levels of poverty and political instability, as well as the rival strategic and economic interests of the British government, which held British Honduras (later Belize) and had a protectorate over Mosquitia.

Early legal agreements On August 26, 1849, the Nicaraguan government signed a contract with the United States businessman Cornelius Vanderbilt. It granted his Accessory Transit Company the exclusive right to construct a waterway within 12 years and gave the same company sole administration of a temporary trade route in which the overland crossing through the isthmus of Rivas was done by train and stagecoach. The temporary route operated successfully, quickly becoming one of the main avenues of trade between New York City and San Francisco. Civil war in Nicaragua and an invasion by filibuster William Walker intervened to prevent the canal from being completed.

Continued interest in the route was an important factor in the negotiation of the Clayton–Bulwer Treaty of 1850. The canal idea was discussed seriously by businessmen and governments throughout the 19th century. In 1888, a bill was proposed in the United States House of Representatives to incorporate a Nicaragua Canal company.Galveston Daily News, December 26, 1888, p 8 In 1890, the American-owned Nicaragua Canal Construction Company held its third annual meeting, while brush was being cleared along the canal route. Many workers fell ill and were hospitalized due to tropical illnesses.Los Angeles Herald, Volume 34, Number 68, 20 June 1890

In a letter sent to the Nicaragua Canal Board in 1895, Swiss geographer and nearby Costa Rica resident Henri François Pittier warned that construction of the project would be difficult to carry out, as earthquakes and heavy rainfall were common in the country. Though Pittier did not believe earthquakes alone could hamper any future construction, he acknowledged that an earthquake or any other seismic activity, for that matter, would bring catastrophic landslides if carried out in areas where soil is soaked with significant amounts of water. However, Pittier also suggested that a study could be conducted in the country's western isthmus between Lake Nicaragua and the Pacific Ocean, as rainfall was less common in this part of the country.

Canal commissions In 1897, the newly named United States Nicaraguan Canal Commission proposed the idea of building the canal. The Nicaraguan Canal Commission carried out the most thorough hydrological survey yet of the San Juan River and its drainage basin, and in 1899 concluded that an interoceanic project was feasible at a total cost of US$138 million. At the same time, the Geological Society of America published the "Physiography and Geology of Region Adjacent to the Nicaragua Canal Route" in its Bulletin in May 1899, which remains one of the most detailed geological surveys of the San Juan River region..

In 1901, the US's Isthmian Canal Commission of 1899 estimated that the cost of building a canal would be $189 million in Nicaragua versus $184 million—$144 million plus $40 million as a fair price to buy the French Panama Canal Company's incomplete work—in Panama. However, the commission recommended the Nicaragua route because the French Panama Canal Company demanded an "unreasonable" price of $109 million rather than $40 million for its incomplete work. After learning that the commission would recommend the Panama route to the US Congress if the price were reduced, in 1902 the French company agreed to sell for $40 million, causing Congress to settle on Panama rather than Nicaragua.

In the late 19th century, the United States government negotiated with President José Santos Zelaya to lease the land for the construction of a canal through Nicaragua. Luis Felipe Corea, the Nicaraguan minister in Washington, wrote to United States Secretary of State John Hay expressing the Zelaya government's support for such a canal. The United States signed the Sánchez–Merry Treaty with Nicaragua in case the negotiations for a canal through Panama fell through, although the treaty was later rejected by John Hay.

Lobbying efforts against the Nicaragua Canal Before Corea completed a draft of the Nicaragua proposal, Congress was considering the Spooner Act to authorize the Panama Canal. In addition to the promise of earlier completion of the Panama Canal, opponents of the Nicaraguan canal cited the risk of volcanic activity at the Momotombo volcano. They favored the construction of a canal through the Isthmus of Panama.

In 1898, the chief of the French Canal Syndicate (a group that owned large swathes of land across Panama), Philippe Bunau Varilla, hired William Nelson Cromwell to lobby the United States Congress for the Panama Canal. In 1902, taking advantage of a year with increased volcanic activity in the Caribbean Sea, Cromwell planted a story in The New York Sun reporting that the Momotombo volcano had erupted and caused a series of seismic shocks. This caused significant concern about its possible effects on a Nicaraguan canal.

Cromwell arranged for leaflets with stamps featuring Momotombo to be sent to every Senator as "proof" of the volcanic activity in Nicaragua. An eruption in May 1902 on the island of Martinique resulted in 30,000 human fatalities. This catastrophe persuaded most of the United States Congress to vote in favor of constructing the canal in Panama, leaving only eight votes in favor of Nicaragua. The decision to build the Panama Canal passed by four votes. Cromwell was paid US$800,000 for his lobbying efforts.

Nicaraguan president Zelaya later tried to arrange for Germany and Japan to finance the building of a canal that would traverse the Zelaya Department in Nicaragua. Having settled on the Panama route, the United States opposed this proposal.

After the Panama Canal (1910–1989) Since the Panama Canal opened in 1914, the Nicaragua route has been reconsidered. Its construction would shorten the water distance between New York and San Francisco by nearly . Under the Bryan–Chamorro Treaty of 1916, the United States paid Nicaragua US$3 million for an option in perpetuity and free of taxation, including 99-year leases of the Corn Islands and a site for a naval base on the Gulf of Fonseca.

In 1929, the United States Interoceanic Canal Board approved a two-year detailed study for a ship canal route, known as the Sultan Report after its author, the United States Army engineer Colonel Daniel Sultan. From 1930 to 1931, a United States Army Corps of Engineers survey team of 300 men surveyed the route of a future canal, called the Forty-Niners route because it followed closely the route that miners took in the 1840s California Gold Rush. Sultan estimated that the proposed canal would be three times longer than the Panama Canal, have larger locks, and cost twice as much. However, Sultan also acknowledged that he and his team also encountered problems due to heavy rainfall and poisonous wildlife. Army engineers on the project included future Manhattan Project engineers, lieutenants Leslie Groves and Kenneth Nichols, who also assisted in recovery after the 1931 Nicaragua earthquake. In Managua, they carried out extensive demolitions to save portions of the city.

Costa Rica protested that Costa Rican rights to the San Juan River had been infringed, and El Salvador maintained that the proposed naval base would affect both it and Honduras. Both protests were upheld by the Central American Court of Justice in rulings that were not recognized by either Nicaragua or the United States. Both nations repealed the Bryan–Chamorro Treaty on July 14, 1970.