Thomas Harris (1895 – 18 February 1974) was a prominent Fianna Fáil politician from the town. A native of Cloncurry, near the Meath border, he was raised in Prosperous by his aunt Elizabeth Tierney. As a young man Thomas Harris had joined the Gaelic League while in school in Prosperous and subsequently joined the Irish Republican Brotherhood, County Kildare. Harris fought with the Maynooth contingent in 1916 Easter Rising in Dublin and was imprisoned in Frongoch, Wales until August 1916. Harris was later Captain of the Prosperous Company in 1917 and later Vice-Commandant North Kildare Battalion of the Irish Republican Army in 1921.