American Classics for the Elementary Crowd

We are coming up on a year of American Studies for homeschooling. Our oldest is 7 years old and is a history aficionado. I'm looking for some good books to read aloud to all of our children, but are challenging, too.

What recommendations do you have for such things? Specifically, I'd like things written perhaps by early presidents or about them. The life of pilgrims, pioneers, immigrants.

We've read the entire Laura Ingalls series as well as many of the Childhood of Famous Americans series. We're hungry for more, and I want the opportunity to start reading them myself over the summer before reading them to our children this fall.

Thank you for your help!