John Capen was born on March 23, 1818, in Goshen, Vermont, to Nathan and Mary Capen. He married Adeliza Child in early 1847, and their daughter Flavia was born around 1868. He supported the Free Soil Party, and voters elected him to the state legislature in 1848. By joining the party, he explained in August 1849, he “did not intend to sacrifice the first Whig principle, and I never adopted a Democratic one.” He vowed that his “future course will be to support men that have maintained a consistent course in opposition to the Annexation of Texas.”
By the early 1850s, he had rejoined the Whig Party. He received an appointment as a postmaster in June 1850 under President Zachary Taylor, and he was elected to the state legislature as a Whig in 1853. By 1856, he had joined the Republican Party. A local writer described him as a “man of good ability and strict integrity.”
By 1860, he was working as a “lumberman” in Goshen, and he owned $3,600 of real estate and $435 of personal property. He moved to Brandon, Vermont, in the 1860s, and by 1870, he owned $6,000 of real estate and $1,500 of personal property. He died of typhoid fever in Brandon on January 5, 1878.