The Rochester Public Library recently added the 1874 Atlas of Ontario Co., NY to their collection of digitized books. This atlas is in PDF format. I like the PDF format because you can make a PDF as large as you want. This atlas is one that shows where homes of people are located. Also the maps show schoolhouses, churches and cemeteries.
This atlas is too early to find any of my relatives. They moved to Ontario County much later. How about you? Do you have any relatives that lived in Ontario County in 1974?