The true purpose of this activity is to introduce students to a five-step EDP (engineering design process). In this chapter, second graders design, build, test, and improve tools to map a waterway, and the design activities are described in detail as they evolved over a period of five years. A model is provided for teachers in the elementary grades who wish to replicate the process in their own settings. This design challenge engages students in conversations about what it means to be “measurable” and encourages them to examine what is “measurable” about a river. This guided-inquiry activity also promotes collaboration and sets the tone for a year of hands-on exploration with real world applications. A materials list, teacher background information, and outcomes are provided. This book selection includes the Table of Contents, Introduction, References, Internet Resources, and Index.