Devin Burghart and Leonard Zeskind are devoted to studying the Tea Party, its supporters and its effect on American society. An integral part of that study is working with Tea Party data- in this case, membership data for different Tea Party groups. Take a look at the viz below to see membership across the country.
Although this viz does not normalize for the overall population, it is clear that there is at least some membership in nearly every city across the country.
Check out more Tea Party statistics at Tea Party Nationalism.