Before getting to the readers, visit this Famous Americans site where elementary students learn facts to help break themselves out of digital escape rooms. (Fun puzzles for kids to solve). They'll learn about Helen Keller, Ben Franklin, Rosa Parks, and a bunch of others.
And now for the readers. The following is a list of Harcourt, Macmillan McGraw-Hill, and Scott Foresman biographies and historical readers for grades 2 - 6. Listed alphabetically; download for free:
Lewis and Clark