Son of Francis S. and Clara (Turrill) Hemenway, Asa Hemenway (1810-1892) was born in Shoreham, Vermont, on July 6, 1810. Hemenway graduated from Middlebury College in 1835, and from the Andover Theological Seminary in 1838. He was ordained in 1839.
Shortly after his ordination, Hemenway was appointed by the American Board of Commissioners for Foreign Missions as a Missionary at Bangkok, Siam. In 1839, Hemenway sailed for Bangkok with two other Middlebury alumni, Jesse Caswell (Class of 1832) and Lyman Peet (Class of 1834). Hemenway was the only classmate to return to the United States when the Siamese mission closed in 1850, Caswell having died in Siam and Peet moving on to the Chinese mission until 1871.
Following his return to Vermont, Hemenway served as pastor of the Congregational church in Cornwall, Vermont (1850-1851), Ripton, Vermont (1851-1860), Keeseville, New York (1860-1864), Mooers, New York (1864-1869), West Hartford, Vermont (1869-1871), and East Chazy, New York (1871-1872). Hemenway married Lucia Hunt on April 14, 1839 and together had two sons and a daughter. Hemenway died in Manchester, Vermont, on February 26, 1892.