I agree with 1956BD about Fever 1793. It is a great book about Yellow Fever in Philadephia, and the kids can relate to the main character. Also, I am David is a great book. It is about a boy who escapes from a concentration camp and makes his way across Europe.
Oops...I just read your message about picture books. Sorry. I got carried away. I like the picture books by Jean Fritz - Can't you make them behave King George...etc