The U.S. has imported millions of barrels of oil every day for more than three decades — but the flow of dollars and fuel has fluctuated over time. How to illustrate such a massive amount of trade over time? With a new map from the Rocky Mountain Institute and Google.org, which visually lays out all the data related to the oil imported into this country from 1973 onward. Admittedly, we always love a good map (101 Cleantech Startups, Biofuels Deathwatch or Coal Deathwatch, anyone?), but this one ranks among the infographic elite.Pretty cool. Allows you to easily see where the US has gotten its oil and how it has changed over the years.