Tehuantepec (tē-wän'tē-pĕk'), an isthmus of Mexico, between the Bay of Campeche on the Gulf of Mexico and the Bay of Tehuantepec on the Pacific Ocean. Its narrowest part is 130 miles wide. It contains lakes, lagoons and Coatzacoalcos and Tehuantepec Rivers. One of the several plans to join the Atlantic and Pacific by a ship-canal proposed crossing this peninsula, in part by deepening and widening Coatzacoalcos River. The Mexican government on Jan. 23, 1907, opened its interoceanic railway (192.42 miles long) from the mouth of the Coatzacoalcos to the Pacific port of Salina Cruz. It saves 10,797 miles from New York to San Francisco through the Straits of Magellan.