The Association of Statisticians of American Religious Bodies conducts The U.S. Religion Census: Religious Congregations & Membership Study (RCMS). It is a county-by-county enumeration of religious bodies in the US. The recent survey done in 2010 captures the demographic spread of Muslims in US through different statistics.
The adjacent chart shows the penetration of Muslims across various counties of US. As can be seen, the Muslim presence is more widely spread on the Eastern side of the country. On the Western side, most of the presence is on the Coastal side.
Also, Muslims tend to stay in the metropolitan areas compared to the rural counties.