Spatial inequalities leave micropolitan areas and Indigenous populations underserved by informal STEM learning institutions.

Informal learning institutions (ILIs) create opportunities to increase public understanding of science and promote increased inclusion of groups underrepresented in Science, Technology, Engineering, and Math (STEM) careers but are not equally distributed across the United States. We explore geographic gaps in the ILI landscape and identify three groups of underserved counties based on the interaction between population density and poverty percentage. Among ILIs, National Park Service lands, biological field stations, and marine laboratories occur in areas with the fewest sites for informal learning opportunities and have the greatest potential to reach underserved populations, particularly in rural or high poverty counties. Most counties that are underserved by ILIs occur in the Great Plains, the southeast, and the northwest. Furthermore, these counties have higher Indigenous populations who are underrepresented in STEM careers. These unexpected geographic gaps represent opportunities for investments in ILI offerings through collaborations and expansion of existing resources.