I've never been to the East Coast, but I try to keep up with the local (western) boxing activity. Currently I reside in Phoenix Az and the number of gyms in the greater Phoenix area is pretty large. There should be many many more fight cards here but...?
Originally I am from So Cal, about 40 miles east of LA, and I am pleased to say that that area is thriving. In the LA area there are numerous promoters running monthly shows and using local talent and in the Inland Empire there are several more doing the same. There are many new gyms that I am not familiar with, as they opened since I left the area. And that part of the world is @ 300 miles from here.
Las Vegas is 230 miles from the IE and the same from Phoenix. Also there seems to be a pretty active boxing enviroment in San Jose/Sacramento, as well as in parts of Utah, including Salt Lake. The state of Washington also appears to have a couple of steady monthly cards.
All in all there is a lot of activity but there should be much more; cards for the 4-6 round fighters, places where guys can learn tom fight. But it is better than it was.