Jim Havey / Alamy

No. 28. Denver

4 of 32

The Mile High City keeps growing, but its environmental roots run deep enough to keep the air and streets clean. After all, with the Rockies staring you in the face from downtown, it’s tough to forget about Mother Earth.

America's Dirtiest Cities 2010

No. 28. Denver

The Mile High City keeps growing, but its environmental roots run deep enough to keep the air and streets clean. After all, with the Rockies staring you in the face from downtown, it’s tough to forget about Mother Earth.

Jim Havey / Alamy

America's Dirtiest Cities 2010

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