 Regarded as a moderate on the slavery issue, Underhill frequently conversed with Alexander H. Stephens, later Vice President of the Confederate States of America, as they sought ways to end slavery which would obtain enough public approval to avert the coming American Civil War.After leaving office Underhill was President of the Mechanics & Traders' Insurance Company in New York City.Underhill died in Whitestone, Long Island in 1866, and was interred was in Woodlawn Cemetery, Bronx.