Messervy began his career in business as a clerk and book-keeper in a large firm in Boston. In 1834, he got a job in St. Louis, Missouri, and by 1839, he was in business for himself, traveling on the Santa Fe Trail and trading with Mexico, including the Mexican territory of Santa Fe de Nuevo México, which later became the American state of New Mexico.
In June 1850, New Mexico adopted a state constitution and Messervy was elected to serve as its first member of Congress. However, Messervy was never officially seated because Congress did not accept New Mexico as a state. The Territory of New Mexico, organized when the Compromise of 1850 passed that September, recognized another man, Richard Hanson Weightman, as New Mexico Territory’s Congressional delegate.
By July, the stress of his three jobs had become too great. He resigned his positions and sold both his house on the Santa Fe Plaza and the Exchange Hotel, Santa Fe’s liveliest venue. He returned to Salem, where he served as mayor from 1856 to 1858, was a director of some local corporations, and was active in scientific and literary societies. He was also a justice of the peace at Salem. Although he had been a Democrat throughout his life, he joined the Republican party during the Civil War. Messervy died after a long illness on February 19, 1886.
William Sluman Messervy may not be a household name, even in New Mexico, but he had an important role in the Americanization of New Mexico, and he was important enough that someone thought to name a street in Albuquerque after him.