[...] Welcome to RadiationNetwork.com, home of the National Radiation Map, depicting environmental radiation levels across the USA, updated in real time every minute. This is the first web site where the average citizen (or anyone in the world) can see what radiation levels are anywhere in the USA at any time (see Disclaimer below). [...]
The map here is just a screenshot. Follow the link to see the real-time map, and the legend that explains what the numbers mean.