The primary-grade years offer a critical opportunity to engage children in understanding and navigating their social world; in discovering the historical events, people, and movements that have shaped contemporary life; in finding--both literally and figuratively--their place in the world; and in understanding how people live together, resolve differences, and work to improve their worlds. Educators have developed a range of innovative and exciting instructional approaches to accomplish these goals. Unfortunately, social studies is more often taught in ways that are not challenging or engaging to young learners. The authors set out to determine the extent to which a specific approach, project-based learning (PBL), would work to teach these skills and values while also engaging students in rigorous learning in both social studies and informational reading/writing. The authors were particularly interested in whether PBL could make a difference in the learning of students from low-socioeconomic status backgrounds, who tend to have fewer opportunities for social studies learning. In their research on PBL, the authors found that it did make a difference in students' learning, and that both students and teachers were engaged by the projects in our units. In this article, the authors briefly describe the general principles driving PBL; introduce our PBL curriculum; share the results of two studies they conducted; and share resources and lessons we learned for educators seeking to develop and teach their own PBL curricula.