In this article, the authors feature the model, Under Control: The Damming of the Missouri River, which was designed to engage middle school students in a real-world geographic issue: investigating the long term environmental, economic and cultural impacts of the 1944 Pick-Sloan Plan, which resulted in the construction of six dams on the Missouri River during the mid-1900s. This topic was selected because the Missouri River is one of the most important physical geographic features in South Dakota and the region. A wiki, a set of expandable web pages that can be edited by anyone within the learning community, was used in the Under Control project to promote critical inquiry and collaborative problem solving across the eleven geographically dispersed classrooms that participated in the curriculum project. This article describes (a) the rationale for using a wiki, (b) the organizational and managerial structure employed, and (c) the professional development program provided to teachers preceding and during project implementation. Finally, lessons learned are presented along with recommendations for using a wiki in a large, student-centered curriculum project. (Contains 3 figures.)