Historical clue formulations

• New York lake that's the source of the Susquehanna River — 2023-05-17
• County or lake of Cooperstown, N.Y. — 2014-02-16
• County of Cooperstown, N.Y. — 2007-12-16
• Lake that James Fenimore Cooper called Glimmerglass — 2007-06-10
• Cooperstown's ___ Lake — 2006-11-22