Three additional counties in the state, as well as three in Alabama and one each in Georgia and Maryland, rounded out the bottom of the list. Below is an interactive map with the county-by-county ...

When there's wildfire smoke in Massachusetts, it's usually coming from thousands of miles away in Canada or the west coast.

According to 2015 census estimates, half of the US population lives in these 143 counties (ranked by population): Los Angeles County, California Cook County, Illinois Harris County, Texas Maricopa ...