Indian tribes

       There are currently 562 indian tribes that are federally recognized. Out of the 562, 229 of the tribes are in Alaska.  The remaining ones are in 33 other states. Not all tribes are federally recognized, the ones that are federally recognized are the ones recognized by the United States Bureau of Indian Affairs (BIA). Most of the tribes are recognized, because it is very important to the members of the tribe to have their tribe to have their recognized. This is because if the tribe is not federally recognized then they do not qualify for special federal and state programs, social services, and funding. It also validates their "tribal sovereignty".  The process is not easy however, there are many guidelines.
      Tribes are often very large, they have over 75 or so people most of the time. The need for so many people is because of the large number of jobs. Today there are not as many jobs but there are still a lot of people in a tribe because that was the way it used to be.

Sources:
 http://www.ncai.org/about-tribes/indians_101.pdf
http://www.californiaindianeducation.org/tribes/faq/
http://www.muckleshoot.nsn.us/multimedia/we-are-muckleshoot.aspx