What is the ARDA?

It's the Association of Religion Data Archives. This site (funded by the Lilly Endowment, the Templeton Fund and Penn State University) is an amazing source, just packed with statistical information of all kinds :

• Find membership data for every county, state, and urban area in the United States, based on the Religious Congregations and Membership Study collected by the Association of Statisticians of American Religious Bodies, the most complete census available on religious congregations and their members.
  
  
• Access the latest in religion research, national surveys, demographic patterns, and changes over time. Obtain detailed information and family trees for over 400 U.S. religious denominations.
  
  
• View maps of the social, economic, demographic, and religious landscape of the United States, all the way down to the neighborhood level. You can even generate a summary report using a variety of options.

And much more! I often get statistical or demographic questions at the Ref Desk, and I tell people, "If you can't find it on ARDA, you probably won't find it at all." Check it out!

http://www.thearda.com/

Paula