Through the centuries of European and American involvement in Central America, several routes were considered and eventually discarded as an option to link the Pacific and Atlantic oceans. The first surveys were done by the Spanish in the 16th century and recommended routes that would remain for centuries the most viable options for a transoceanic canal. The Panama and the Nicaragua routes were the top contenders. All these routes also served to some extent as portage routes. By the mid 19th century, the commercial (growth in trade and larger ships) and technical (heavy machinery) conditions incited renewed interests and more comprehensive surveys of the canal routing options:
- The Panama Canal route was selected as the most suitable because of the shortest distance and thus the lowest construction cost (highest elevation at Lake Gatun, which is 85 feet / 26 meters above sea level). In 1881 the French began construction of the canal but were forced to abandon the project in 1889 in part due to engineering difficulties in part because of a very high mortality rate among workers due to tropical diseases such as malaria. This existing sunk cost was a further incentive for the United States to continue what had already begun by acquiring in 1904 the failed French concession in Panama.
- The Lake Nicaragua route, which was also considered a possibility, particularly in 1884 when the governments of the United States and Nicaragua agreed upon a memorandum to build a canal. However, the project was abandoned in part because of prohibitive construction costs. There were also concerns about the volcanic activity of mount Conception that sits in the middle of Lake Nicaragua and that has been recursively active. Lake Nicaragua is 107 feet (32.7 meters) above sea level. However, access to the Pacific Ocean from Lake Nicaragua must pass through a coastal mountain range where the lowest point is around 185 feet.
- The Isthmus of Tehuantepec route, which represents the shortest distance between the Gulf of Mexico and the Pacific Ocean. Several routes were investigated in the 19th century to build a canal, but the distances involved made this option less attractive than the others. In the 1880s, a plan was devised to build an interoceanic ship railway through the Isthmus that would carry ships on a six tracks rail corridor, but such a plan was abandoned. In 1907 the Tehuantepec National Railway, which linked the ports of Coatzacoalcos (Gulf of Mexico) and Salina Cruz (Pacific), was opened. It offered an efficient transoceanic alternative that at its peak (1913) carried 850,000 tons of cargo. However, after the opening of the Panama Canal in 1914, the railway lost its competitiveness and ceased to be used as a transoceanic option.
- The Darien route. Interests for the Darien route take their origin in the failed attempt by the Scots to establish a colony in 1698, an attempt in part motivated by a possible transoceanic canal. In the 1850s an expedition sponsored by England, France, and the United States was sent to survey a potential canal route across the isthmus of Darien, from Caledonia Bay, on the Caribbean coast, to the Gulf of San Miguel, on the Pacific. Although both sides were judged to have excellent harbor facilities, a practical path across the 65 km isthmus could not be effectively assessed.
- The Gulf of Uraba route. An option that was surveyed, but judged to be too expensive, particularly since it would have necessitated the construction of a ship tunnel.