He was born in Stonington, Connecticut. He studied at Tracy's Academy in Norwich and at Yale University from 1838, but ill-health prevented his graduation, he was enrolled in 1850 and received an honorary LLD in 1871. He settled in Hartford and was assistant-secretary of state of Connecticut in 1847-1852, Connecticut state librarian in 1854, assistant-secretary again in 1858-1861, and (Republican) secretary of state in 1861-1866. He was a prominent member of the Connecticut Historical Society, of which he was president from 1863 to 1889. He was elected to the National Academy of Sciences in 1872. He died in Hartford.
His works include a number about the history of Connecticut, such as Historical Notes on some Provisions of the Connecticut Statutes (1860-1861) and The True Blue Laws of Connecticut (1876). His studies of Native American dialects led to The Composition of Indian Geographical Names (1870), The Best Methods of Studying the Indian Languages (1871), Indian Names of Places in Connecticut (1881) and other similar works.
His brother was the author Henry Clay Trumbull.