Almon Underwood was born in Monson, Massachusetts, on May 15, 1809, the son of Nehemiah Underwood and Polly Shaw. He attended Amherst College from 1827-1829 and graduated from Union College in 1830. Underwood lived in Troy, New York, in the 1830s, and was ordained in New York City on December 6, 1837. After preaching in Poughkeepsie, New York, for several years, he moved to Newark, New Jersey, where he led the Free Presbyterian Church. Underwood married Henrietta Platt on December 18, 1834; they had two children: Henrietta Platt (b. 1837) and Henry Beman (b. 1839). After his wife's death in 1842, Underwood married Elizabeth Scofield on October 23, 1844. They had three children: Rufus Scofield (b. 1846), Charles Finney (b. 1849), and Ella Elizabeth (1856-1857). Almon Underwood died on June 10, 1887.