Well, the air in Minnesota is pretty clean, and I grew up there, so I'm identifying  with the rankings there instead of my current state of residence, which got surprisingly low grades.

The annual State of the Air report describes levels of ozone and particle pollution (year-round and 24 hour increments) in monitoring sites across the United States in 2005, 2006, and 2007. Apparently the air quality in the U.S. could use some improvement.

Good news and bad news: the good news is, some cities are reducing ozone (LA, Houston) and particle pollution levels (Pittsburgh, Cincinnati, Atlanta). The bad news is other cities are taking their place at the tops of the lists in ozone (Phoenix, Las Vegas, and Cincinnati) and particle pollution (Bakersfield, Houston). Note Houston and Cincinnati traded one evil for another. Pittsburgh took the crown for the highest short-term (24 hour) levels of particle pollution, even though it reduced its overall annual average levels.

On the whole, six out of ten people (61.7%) in the United States population lives in counties that have unhealthful levels of either ozone or particle pollution, the report says. Almost 186.1 million Americans live in the 525 counties where they are exposed to unhealthful levels of air pollution in the form of either ozone or short-term or year-round levels of particles.

Which city has the cleanest air? Fargo-Wahpeton, ND-MN, which was top clean city on all three lists (the only one to do so). Seventeen cities appeared on two of the three lists of cleanest cities: Billings, MT; Bismarck, ND; Cheyenne, WY; Colorado Springs, CO; Farmington, NM; Ft. Collins, CO; Honolulu, HI; Lincoln, NE; Midland-Odessa, TX; Port St. Lucie, FL; Pueblo, CO; Redding, CA; Salinas, CA; San Luis Obispo, CA; Santa Fe-Espanola, NM; Sioux Falls, ND; and Tucson, AZ.

Check out your county and state rank, grades, who are the best and the worst, test your pollution knowledge, and more at the State of the Air site.