I thought I had the whole day free today. That was before I discovered The Davies Project and their Database of American Libraries before 1876.
This database covers institutional and commercial libraries that existed in what is now the continental United States from the time of first settlement through 1875. It records nearly 10,000 libraries. The end-date of 1876 is important because in that year the United State Bureau of Education published its first comprehensive, national listing of libraries, entitled Public Libraries in the United States of America: Their History, Condition, and Management. Special Report. Part. 1 [bespacific]