The History Center of Tompkins County is a good source for information about events and the changing landscape of the Ithaca area over time. Although the Center is not open to the public during COVID, research services are still available and appointments can be made.
The History Center has also launched HistoryForge to bring together maps, photographs and other resources to provide a better idea of life in Ithaca over the years. The interface allows you to search by place and person.
Cornell's Rare and Manuscript Collection (RMC) maintains files of original documents, letters and other documents related to Cornell University history. Items can be requested in advance to be drawn from the special collections vault and an appointment can be made to view those materials in the RMC reading room. RMC has a number of collections including one on Regional History.