@bythewell - I think a problem is that fundamental elementary lesson plans go about teaching the wrong way. They focus on activities that are supposedly "fun" (and sometimes are, sometimes aren't) and hope to sneak in knowledge at the same time.
But a student doing a crossword is learning how to do crosswords. They aren't learning about American history, even if the words are related to that.
If you want them to learn about American history you have to get them to do tasks from that era or relating to it. Writing a newspaper that would reflect the views of a specific colony, for example. Making a video presenting the daily activities of a specific Native tribe.
These are interesting tasks (particularly if you allow the students some choice in which ones they do) and will involve enough research into details that the students will end up learning everything they need to know.