The Union Agricultural Society of Barkhamsted, Colebrook and Hartland, Inc. was organized in September 1909 and incorporated on October 8, 1909 for the purpose of holding an agricultural fair in Riverton each year.
The first fair was held on the schoolhouse grounds on October 12, 1909 with an estimated attendance of 3000. Livestock and crops were exhibited and judged, drum corps and bands provided entertainment, games were played, and a tradition began.
In 1947 it was voted to expand the fair from just Columbus Day to a two-day event.A meeting was held on August 28 of 1955 to examine the damage done by the flood of August 19. The poultry and cattle barns were entirely washed away, as well as the poultry coops, the bandstand and vaudeville platform, the toilets and ticket offices, driveways and pulling ring. Silt and sand covered what was left of the lower end of the grounds. All the lumber for siding the new pole barn that was being built was gone. Some were in favor of disbanding, but finally a motion was made and passed to continue, and the cleanup and rebuilding began.