Career
He represented 1st Kings from 1879 to 1882 and 2nd Kings from 1886 to 1893 in the Legislative Assembly of Prince Edward Island as a Liberal and then a Conservative member. He was born in Bay Fortune, Prince Edward Island, the son of William Underhay and Marianne Withers. Underhay was a justice of the peace and also served as postmaster at Grand River.
He was the head of the Independent Order of Good Templars in the province.
Underhay was an unsuccessful candidate for a seat in the province"s legislative council in 1874 and was defeated when he ran for reelection in 1882.