In this article, the authors describe how they used primary and secondary sources related to the Indian Removal Act to develop a learning activity in which students analyze, corroborate, and synthesize primary sources. Using the free, online authoring tool, UDL Book Builder, they were able to develop on-demand digital scaffolds that temper an engaging and challenging approach to critical thinking with instructional support. A key aspect of this program is the digital agents that educators can program to model critical thinking about primary sources. The authors include the text they developed for the agents' think-alouds learners can access. Finally, the authors end with ideas for resources teachers can use to access historical arguments for additional history topics. (Contains 3 figures, 1 table and 1 note.)