A bunch of researchers with Purdue University's Vulcan Project have created the most detailed database yet of where all the human sources of carbon emissions in the United States are. They've mapped it down to the level of individual power plants, factories, roadways, neighborhoods... it's all very handy. The short video graphing out the results is fun to watch, especially as the emissions ebb during the night. I don't think there are many surprises as to where the pollution comes from, though:
You can download the county-by-county data here, if you're so inclined.