Hilsman remained active in local politics, where he was a member of the Democratic Town Committee in Lyme for over two decades. During the 1990s he led a letter-writing campaign to the Connecticut State Police on behalf of safer street speeds in Lyme. He continued to publish books on a variety of subjects into his eighties. He and his wife later lived in Chester, Connecticut, and Ithaca, New York. Through 2014, Hilsman was still listed as a professor emeritus at Columbia.