He was born in New Haven, Connecticut, son of Ralph Isaacs Ingersoll, a New Haven lawyer who also served in the state House of Representatives, the United States Congress, and as United States Minister to Russia and as the mayor of New Haven, and of his wife, Margaret, née Van den Heuvel. He graduated from Yale College at the age of nineteen in 1840. He visited Europe aboard the United States frigate Preble, commanded by his uncle, Captain Voorhes, for two years, and returned to Yale Law School, graduating in 1844. He was admitted to the bar in 1845 and became the law partner of his father. He served in the state legislature as a democrat. Elected governor of Connecticut in 1873, he was re-elected yearly until 1876, when he declined nomination.
His wife was Virginia Gregory, daughter of Admiral Gregory. They had six children. A daughter, Elizabeth married George G. Haven, Jr.
He died in New Haven and was interred at Grove Street Cemetery.