What’s the greatest concentration of muslims in the US?
The entire city of dearborn, MI? 
When they’re in a madrassa?
Thanks. I’m here Tuesday and Thursday evenings after the band. Goodnight.
It would not be the entire city of Dearborn; city hall spent a lot of effort trying to “encourage” them to move elsewhere and I doubt that that has significantly changed in the last couple of years. On the other hand, Southeast Michigan, generally, is probably a good bet.
The American Religious Data Archive website show a census by denomination throughout the U.S., but you have to pick through it to find the information.
Since Muslims (and, increasingly, Christians) do not all register with specific mosques or churches, the figures are probably underreported for the number of adherents. The specifics of the survey can be found at the web pafe of the sponsors, the Glenmary Research Center. (Yes, it is a Catholic outfit, but they are generally regarded as fairly competent in conducting this survey with the caveats that they note on their site.)