Species richness, migration, habitats, ecological niches, adaptations: Concepts such as these come alive when students explore and analyze landscapes, environmental characteristics, and related biological features represented on digital maps. Most students are familiar with navigation tools integrated into smartphone apps but may be surprised to learn that the same mapping technologies are found in biological, environmental, and conservation research. Using maps or tabular spatial data, students can construct powerful scientific arguments grounded in real data. One user-friendly yet powerful mapping tool is ArcGIS Online. GIS stands for "Geographic Information System," which refers to a data management system that captures, processes, and displays spatial data. Teachers and students can use maps provided on the website, build their own from a large repository of online data, or create maps using data they enter themselves. ArcGIS Online is free, fast, and reliable. Research on use of GIS in science and environmental education has documented the challenges as well as opportunities (Barnett et al. 2013). This article describes two cases in which the authors used web-based GIS maps in student inquiry focused on bird habitats, biodiversity, and conservation. The maps and lessons were developed in collaboration with almost 60 teachers who participated in the Crossing Boundaries Project. Each lesson was co-designed with teachers, piloted during professional development workshops, field tested in the classrooms of participating teachers, and continually refined. Each case describes a map, corollary lesson sequence, student investigation highlights, and a teacher's implementation experience. The teacher using the first lesson was teaching a ninth-grade course entitled STEM 9. The teacher using the second lesson was teaching environmental science for grades 11 and 12. In both cases, the teachers were using desktop computers in a wired computer lab. The maps and related resources are available online.