Twilight became a teacher, first in Peru, New York (1824-1828), then Vergennes, Vermont (1828-1829). He was ordained a Congregational clergyman in 1829, but chose to pursue a career in education. Twilight was appointed Principal of the Orleans County Grammar School in Brownington, Vermont and reportedly built the school building eventually known as the Brownington Academy with his own hands. He taught in Brownington from 1829-1847. During that period, he served as a representative to the State Legislature in 1836. Twilight briefly relocated to Canada, teaching in Shipton (1848-1850) and Hatley (1850-1852), before returning to Brownington, where he again taught from 1852-1855.
Twilight married Mercy Ladd Merrill, on April 20, 1826. He died in Brownington, Vermont, on June 19, 1857.Alexander Twilight has been noted as the the first person of color to graduate from an American college, based, in part, on his father's racial identity. Recent scholarship has complicated the history of Twilight's Black identity, without diminishing his achievements as a student and alumni of the College.