Continental margins are an important part of the ocean floor. They separate the land above sea level from the deep ocean basins below and occupy about 11% of Earth's surface. They are also economically important, as they harbor both mineral resources and some of the most valuable fisheries in the world. In this article students investigate North America's continental margins using GeoMapApp, a free global topography database. Each student investigates continental margins along the East, West, and Gulf Coasts, determines the nature of these margins, and identifies common morphologic features. Their direct involvement in the collection and interpretation of data encourages conceptual understanding, rather than the simple memorization of facts. The activity focuses on the Blake Plateau and Gulf of Mexico--two areas not typically discussed in textbooks--allowing students to make new, individual observations and collect and organize information. These skills will help them in both science and nonscience classes and in their future careers. This activity is best suited for high school Earth science, geology, oceanography, and environmental science courses. (Contains 2 figures and 11 online resources.)