During the War of 1812, Rochester was an aide-de-camp to Gen. George McClure. After the war, he studied law with his uncle Judge Adam Beatty and with Henry Clay, was admitted to the bar, and began practice in Bath, New York. Later, he removed to Angelica, New York.
He was Secretary to the Special Envoy Extraordinary and Minister Plenipotentiary to Colombia in 1826, and Chargé d'affaires to Central America in 1827–28.[5] He was appointed Chargé d'Affaires of Guatemala on March 3, 1827, and was commissioned to the Republic of Central America. He reached Central America, but returned to the United States without presenting credentials.[5][6]
On April 9, 1832, he married his third wife Eliza (née Hatch) Powers (1800–1885), a half-sister of Gov. Enos T. Throop and the widow of U.S. Rep. Gershom Powers. Together, William and Eliza were the parents of:[2]
Eliza Hatch Rochester (1833–1868), who married Augus B. Fitch[2]