As the United States strives to achieve energy independence, students need to be literate about energy and environmental issues. In this article, the authors present a lesson about the nation's electricity resources that is part 1 of a free, comprehensive unit on coal and energy that is available online (http://tinyurl.com/coalenergyunit). The comprehensive unit, which was developed by graduate students supported by the Transforming Earth System Science Education project at Penn State University, contains inquiry-based lessons designed to deepen students' understanding of key Earth-science issues. Data on electricity-generation resources in the United States, including both renewable and nonrenewable types, are highlighted within the lesson of part 1. Part 2 of the comprehensive unit includes lessons that address more detail about coal. In both parts of the unit, students learn fundamental information about the development and use of domestic energy sources. The full lesson for part 1 is included here, but both parts of the comprehensive unit are also described. Completion of all or part of the unit will provide an interdisciplinary look at the nation's energy resources. (Contains 4 figures and 1 online resource.)