Born in 1840 in Prince Edward County, Platt attended Fort Edward Military Academy in New York State, the Normal School, Toronto and Victoria College in Cobourg, Ontario.
Graduating there as an M.D., he served as Surgeon with the 16th Battalion, Volunteer Militia during the Fenian Raids in 1866. He was also the first editor/publisher of the Picton New Nation as well as a teacher and school inspector. From 1878 to 1892 he was the Liberal member for Prince Edward County in the federal parliament.
At Cedarhedge, Platt had two blood-hounds as pets which "the prisoners thought would devour them on slight provocation"! Evidence of the dogs can be seen on the South-west window sill in the gallery on the museum's second floor.
His only child, Garfield, served as the Kingston Penitentiary Surgeon from 1931-1942. Warden Platt died Sept. 27, 1919 at Picton, Ontario.