The Isthmus of Tehuantepec is an isthmus in Mexico. It represents the shortest distance between the Gulf of Mexico and the Pacific Ocean, and prior to the opening of the Panama Canal was a major shipping route known simply as the Tehuantepec Route. The name is taken from the town of Santo Domingo Tehuantepec in the state of Oaxaca, which in turn comes from the Nahuatl tecuani-tepec ("jaguar hill").
The isthmus is 200 km (125 miles) across at its narrowest point from gulf to gulf, or 192 km (120 miles) to the head of Laguna Superior on the Pacific coast. The Sierra Madre breaks down at this point into a broad, plateau-like ridge, whose elevation, at the highest point reached by the Tehuantepec railway at Chivela Pass, is 224 m (735 ft). The northern side of the isthmus is swampy and densely covered with jungle, which has been a greater obstacle to railway construction than the grades in crossing the sierra.
The whole region is hot and malarial, except for the open elevations where the winds from the Pacific Ocean render the weather comparatively cool and healthy. The annual rainfall on the Atlantic or northern slope is 3,960 mm (156 in) and the maximum temperature about 35 degrees Celsius (95 degrees Fahrenheit) in the shade. The Pacific slope has a light rainfall and drier climate.
The narrowness of the isthmus, and the gap in the Sierra Madre, allow the trade winds from the Gulf of Mexico to blow through to the Pacific. Normally, these winds are not particularly strong, but periodically, a surge of denser air originating from the North American continent will send strong winds through the Chivela Pass and out over the Gulf of Tehuantepec on the Pacific coast. This wind is known as the Tehuano.
Since the days of Hernán Cortés, the Tehuantepec isthmus has been considered a favorable route, first for an interoceanic canal, and since the 19th century for an interoceanic railway. Its proximity to the axes of international trade gives it some advantage over the Panama route; the Isthmus of Panama, however, is significantly narrower, making for a shorter traversal, even if the canal is farther from trade routes. See also: Panama Canal, Nicaragua Canal.
The Gadsden Purchase in 1853 included a provision allowing the U.S. to transport mail and trade goods across the Isthmus of Tehuantepec via a plank road and railroad. The 1859 McLane-Ocampo Treaty, which Benito Juárez signed but was never ratified by the United States Congress, would have given the US extensive transit rights along the same route.
When the great cost of a canal across the isthmus compelled engineers and capitalists to give it up as impracticable, James B. Eads proposed to construct a quadruple track ship-railway, and the scheme received serious attention for some time. Then came projects for an ordinary railway, and several concessions were granted by the Mexican government for this purpose from 1857 to 1882. In the latter year the Mexican government resolved to undertake the enterprise on its own account, and entered into contracts with a prominent Mexican contractor for the work. In 1888 this contract was rescinded, after 108 km (67 mi) of road had been completed. The next contract was fruitless because of the death of the contractor, and the third failed to complete the work within the sum specified (2,700,000). This was in 1893, and 60 km (37 mi) remained to be built. A fourth contract resulted in the completion of the line from coast to coast in 1894, when it was found that the terminal ports were deficient in facilities and the road too light for heavy traffic. The government then entered into a contract with the London firm of contractors of S. Pearson & Son, Ltd., who had constructed the drainage works of the valley of Mexico and the new port works of Veracruz, to rebuild the line and construct terminal ports at Coatzacoalcos on the Gulf coast, and at Salina Cruz on the Pacific side. The work was done for account of the Mexican government. Work began on 10 December 1899, and was finished to a point where its formal opening for traffic was possible in January 1907.
The railway is 308 km (192 mi) long, with a branch of 29 km (18 mi) between Juile and San Juan Evangelista. The minimum depth at low water in both ports is 10 m (33 ft), and an extensive system of quays and railway tracks at both terminals affords ample facilities for the expeditious handling of heavy cargoes. The general offices, shops, hospital, &c., are located at Rincón Antonio, at the entrance to the Chivela Pass, where the temperature is cool and healthful conditions prevail. At Santa Lucrecia, 175 km (109 mi) from Salina Cruz, connection is made with the Veracruz & Pacific railway (a government line), 343 km (213 mi) to Córdoba, Veracruz, and 500 km (311 mi) to Mexico City.