He had a general merchandising establishment there, along with a stock farm to breed and train race horses.
[1] When George W. Aldridge was cementing his power as the leader of the Monroe County Republican Party, Denniston served as his assistant.
[2] In 1890, Denniston was elected to the New York State Assembly as a Republican, representing the Monroe County 3rd District.
They helped build the Rochester Public Market in 1904 and the Cobbs Hill Reservoir in 1906.
Their three sons were Charles W., Frank J., and Louis F.[2] Denniston died at home in Rochester on March 11, 1936, the day after his 86th birthday.