 When Taylor won the election, Letcher's friend John J. Crittenden recommended Letcher for the post of postmaster general; Taylor declined this suggestion, but instead appointed Letcher as the United States envoy and minister to Mexico.Letcher arrived in Mexico City on February 3, 1850.Letcher's primary responsibility was negotiating a treaty to protect the interests of some American citizens who had purchased the rights to construct a line of transit on the Isthmus of Tehuantepec.