Nothing comes closer to "the truth" than a primary source, even a primary source with wart--biases, narrow-minded interpretations, and historical inaccuracies. Students who learn to apply critical thinking to the analysis of primary sources also learn to situate sources within the broader historical context, test hypotheses, form their own opinions, and argue for their conclusions. Primary sources are all about critical thinking, and as such, the skills needed for primary source analysis fit into nearly every expectation for the 21st century classroom. Web 2.0 tools merely exploit the underlying thinking skills. In this article, the author explains how primary sources and Web 2.0 concepts complement each other to promote learning among students.