Concern over the declines of pollinator populations during the last decade has resulted in calls from governments and international agencies to better monitor these organisms. Recent studies of bee diversity in urban environments suggest that cities may contain significant amounts of bee species, even greater than surrounding agricultural areas, and in some occasions comparable to natural habitats. We conducted a three-year survey of bees in the city of St. Louis, MO. Like many other post-industrial cities in the United States, St. Louis is considered a shrinking city, with many vacant lots and unoccupied structures, mostly in the urban core. We sampled a broad range of habitats throughout the growing seasons of 2013 to 2016, e.g., vacant lots, city parks, community gardens, and urban farms, using aerial netting. This resulted in over 7,700 specimens. Data from other surveys, e.g., BioBlitz, and personal collections was also utilized in developing the species list. These data were supplemented with inspections of entomological collections from institutions in the state and the scientific literature. We identified a total of 198 species of bees from five different families that occur in the city. Only nine of the bee species present in the city are non-natives. The city of St. Louis currently hosts nearly 45% of the bee diversity of the state, likely making it one of most species-rich cities relative to its state's total bee fauna in the country. This represents a great natural resource that must be better understood, and has potential conservation implications.