I’m not going to go into all the details here, and I’d really encourage you to read Kevin’s post about it — he explains it completely with several screenshots. Basically, students choose images from United States history and are guided through a critical thinking process about it.
The language, and images, are very accessible to English Language Learners. It’s a great site. However, it would be an extraordinary site if one of the early steps of the process paid a little more attention to explicit vocabulary instruction that would scaffold the rest of the activities.
I’ll be placing the link somewhere on my United States History page.