Mt. Morris, first settled around 1784. It was known as "Allens Hill" and then as "Richmond Hill." The town was formed from the Town of Leicester in 1818. The former Genesee Valley Canal passed through the town.

The area had three major Seneca villages: Little Beard's Town, Big Tree, and Squakie Hill. These settlements were targets of the Sullivan Expedition. Little Beard, or “Spear Hanging Down", was a Seneca chief on the side of Great Britain. His village, Little Beard's Town consisted of about 130 houses. Little Beard participated in the Cherry Valley massacre of 1778, and presided over the torture and death of Boyd and Parker, captured scouts of the Sullivan Expedition of 1779. Subsequently, Little Beard's Town was destroyed by the American forces. Mary Jemison, then a resident of the village, fled with the natives to more secure villages. The modern town of Cuylerville was built at the spot.
Little Beard was one of the Seneca chiefs signing the Treaty of Canandaigua of 1794. He was also a signatory to the Treaty of Big Tree in 1797. He died as the result of injuries received during a brawl at a tavern in 1806.