Most studies of white-tailed deer (Odocoileus virginianus Zimm.) herbivory focus on a few forb species or single sites in forest plant communities. However, managers require assessments of herbivory impacts across varying deer densities and in multiple plant communities, including wetlands and savannas where there is limited knowledge about the impacts of deer on herbaceous vegetation. During 2008 and 2009, we investigated deer herbivory impacts at six forest preserves near Chicago, Illinois. We sampled 192 browse transects in two forest, two savanna, and two wetland sites; sites were paired within each plant community type based on deer density (i.e., high vs. low). We used plant community metrics (i.e., percent non-vegetated ground cover, species diversity and evenness, and floristic quality) to quantify and compare herbivory impacts on vegetation between preserves. We observed higher grass cover (0.001 < P < 0.012), lower species diversity (0.001 < P < 0.041), and lower floristic quality (0.001 < P < 0.030) in preserves containing higher deer densities (22–29 deer/km²; low-density populations were 6–19 deer/km²) for all three plant community types. Managers should be aware that deer are negatively affecting forest, savanna, and wetland plant communities at densities of > 20 deer/km2 in the Great Lakes region. We further suggest managers use plant community metrics, rather than single indicator species, to monitor deer herbivory.