Baker Library Collection of American Currency
The Baker Library at Harvard Business School has made a great resource available, particularly for those doing research or teaching in American monetary history. It has made available online its digital collection of over 700 pieces of American paper money ranging in date from 1709 to 1878. This collection illustrates the history of American finance and commerce from Colonial times through the Civil War.
The collection can be accessed here: https://curiosity.lib.harvard.edu/american-currency