Ontario County, New York 

 

Summary

Created from Montgomery Co., 27 Jan. 1789.1 Area settled, summer 1789.2 Named for Lake Ontario on northern border.3 Known as “Genesee country.”4 Area historically occupied by Seneca Indians.5 County seat, Canandaigua.6 Population in 1820 about 35,000.7 Population in 1830 about 40,000.8 Erie Canal built near northern boundary.9 Farmington Township (now Manchester Township) in county was location of key events in early Mormon history, 1820–1830.10