My dad has told me for years that Benjamin Rush is one of our ancestors and I'd love to be able to learn more about him. The most I know is that he was a doctor.
Just seeing this now, I am doing a project on Benjamin Rush. A great book is Benjamin Rush: American Gadfly.
Find the website of your local library and go to the online library catalog. Type in the name "Benjamin Rush" (and, if it gives you the option, tell it to look for books whose "Subject" is Benjamin Rush). It will show you a list of books about Rush that you can find at that library.