Assessing the 21st century skills with Library of Congress documents-a new generation of history assessments that includes 55 formative assessments tied to social studies topics. The History Assessments of Thinking (HATs) use collections of documents, photos, paintings, radio broadcasts, and film clips to measure students' historical understandings and critical thinking skills. Interactive scoring rubrics link to sample student responses and many assessments include a "Going Deeper" video that extends teachers' understanding of that task and the historical skills it measures.