George Mason University has posted online four units of study for US History. Each unit is based on images and primary documents. The units are divided by century pre-18th, 18th, 19th, and 20th. Each unit has a selection of images and or documents that are the focus of a series of inquiry based questions. Each item in each unit offers resources for additional study.

Applications for Education
These units could be used as individual student assignments or as group discussions in high school classrooms.
A related resource that could complement the units of study from George Mason University is the Picturing America series from the National Endowment for the Humanities.