The D’Aulaire biographies and A More Perfect Union. We really enjoyed the Holling C. Holling books Tree in the Trail and The Book Of Indians. Also read some Little House on the Prairie.
For more modern world history, we enjoyed The Journey That Saved Curious George. We almost skipped that one in the module 6 guide. But we really like Curious George and the kids seemed to have a good connection with that one, about WW II. Also Chestry Oak, if your library has it. It is oop and expensive.