The known distributions of eastern red bats and western red bats in western North America have changed greatly over the past 2 decades, resulting in inaccurate range maps and uncertainty regarding the presence or probable absence of these species within states and provinces. We obtained capture and specimen records from the western United States and Canada for 276 eastern red bats and for 863 western red bats. We documented the expansion of the range of eastern red bats in northwestern Canada and clarified the northern and eastern limits of western red bat distribution in the United States. We found that the eastern red bat and western red bat exhibit a mostly allopatric distribution, with western red bats mainly inhabiting warmer, drier forested ecoregions at lower latitudes than those inhabited by eastern red bats. A small zone of overlap between the species was identified only in far western Texas, although it is possible that sympatry may be more widespread due to errors on museum specimen labels and misidentification of captured red bats.