May was born in Sandisfield, Massachusetts to Rockwell and Celestia (Underwood) May and moved to Richland, Michigan at the approximate age of twelve. There he worked on the farm and attended district schools. In 1842, he attended the Kalamazoo branch of the University of Michigan (now Kalamazoo College), entered the sophomore class in 1846, and graduated in 1849 from the classical department. During that time he became a member of Alpha Delta Phi.
In 1849, he married Amelia Stryker Kellogg in Sherwood. They had three daughters. After graduating he entered the law office of Lathrop & Duffield in Detroit and in July 1850 was admitted to the bar at the Michigan Supreme Court. The following month he opened an office in Battle Creek, and two years later moved to Kalamazoo forming a co-partnership with Marsh Giddings. In 1854, he was elected prosecuting attorney and served from 1855 to 1862. He also served as school inspector for two years and superintendent of the village schools from 1853 to 1856.
In 1866, May was elected the 18th lieutenant governor of Michigan as well as trustee of the village of Kalamazoo. He served as lieutenant governor from 1867 to 1869 under GovernorHenry Crapo's second term. His brother Charles S. May had also served as lieutenant governor from 1863 to 1865.
In 1868, he was elected to the office of Michigan Attorney General and served from 1869 to 1873 under Governor Henry P. Baldwin. In 1874, he was elected president of the village of Kalamazoo and was re-elected the following year.
Death
Dwight May died in 1880, aged 57. He was buried at Mountain Home Cemetery of Kalamazoo.[citation needed]