Despite the importance of bees as pollinators, for most species little is known about their specific habitat requirements. We quantified suitable habitats for 4,200 bee species known to occur from Colombia through Canada. This covers the entire tropical to tundra ecosystem gradient and encompasses northern Mexico/southwestern United States – a documented hotspot in global bee biodiversity. The gradient examined is extensive enough to represent tropical bees such as meliponines and euglossines, as well as taxa more characteristic of temperate ecosystems such as Bombus. To quantify habitats for this hyperdiverse monophyletic clade distributed across a continental scale, we delineated bee species based on taxonomy, morphology, life history, and habitat preferences. Herein, our research: 1) Defines the boundaries and bee assemblages for the species richness in the Mexico-United States deserts; 2) Documents the changes in bee assemblages as they extend out from this desert biodiversity hotspot; and 3) Assesses whether the combination of taxa and traits in this hotspot are different from regions outside the hotspot. Our findings provide important insights not just into the habitat requirements of Anthophila, but also the evolutionary ecology of the group.