The authors developed and implemented a project for high school geography students that modeled the processes in a site selection analysis using Geographic Information Systems (GIS). They sought to explore how spatial thinking could be fostered by using the MyWorld GIS software that was designed specifically for educational uses. The task posed for the students was to: (1) perform a site selection analysis using GIS to determine the best location for a new business of their choice; and (2) present and justify their ideal location with a PowerPoint presentation. The authors divided the project into four parts that were completed during the course of three 80-minute "block" class periods. Students were given a hand-out with "Think About" and "To Do" prompts for each part and a "Proposal Checklist" on which to record their responses. The MyWorld software proved to be a valuable--though not perfect--tool for this project. Overall, most students found the software easy to use, but they were understandably frustrated when their computers crashed as they ran analyses. The results of this project reveal much about spatial thinking with GIS. Most importantly, the project demonstrates that a powerful geo-analysis tool can be used successfully in a classroom to promote students' spatial thinking. (Contains 1 table and 4 notes.)