The treaty was negotiated by Robert M. McLane, the US Ambassador to Mexico, and Melchor Ocampo, Mexico's Minister of Foreign Affairs. It was signed in the port of Veracruz in Mexico on December 14, 1859, which would have sold the perpetual right of transit to the Isthmus of Tehuantepec to the U.S. for $4 million through the Mexican ports of Tehuantepec in the south, to Coatzacoalcos in the Gulf of Mexico free of any charge or duty, for military and commercial effects and troops. It even required Mexican troops to assist in the enforcement of the rights permanently granted to the U.S.