Denver metropolitan areaThe Denver Metropolitan Area (population 2,109,282 in 2000) has Denver, Colorado with a population of about 500,000 as its core. Intensive urbanization has extended into Jefferson County to the west; Arapahoe County to the south and east; and Adams County to the east and north.
There is some cooperation in the metropolitan area in mass transit, but generally each county and its various towns are self-governing. The character of the various parts of the metropolitan area vary widely with the most prosperous portions being Douglas and Boulder County, with Adams county being the most industrialized of the suburbs.
The entire metropolitan area sits in a valley, the Denver Basin, and suffers from air pollution known colloquially as the brown cloud, building up if the air is stagnant as it often is in the winter.