Anyone who likes maps, religion and useful or odd bits of data will have fun poking around the website created by the Association of Religion Data Archives, which now includes information from the 2010 census. The site allows for all kinds of searches by denomination and region.

For example, the curious can find out what U.S. counties have the highest or lowest percentage of Episcopalians. Coming in first is the Yukon-Koyukuk area of Alaska, where 38 percent of the population consider themselves Episcopalians. (I’m guessing the Episcopalians did some major mission work with native people there.) Next is Dewey County, South Dakota, at 17 percent. (More native missions there?)

You can also find maps showing regional concentration of various groups, such as this one showing the relative concentration of American Baptists in Illinois by county, broken out by adherents and by the number of congregations. I’m not exactly sure what this kind of map is good for, but if you’re someone who loves maps, as I do, it is satisfying to look at.

Perhaps most useful are ARDA’s religious profiles of each county or metro area. Just by typing in a zip code you can pull up an empirical survey and get a sense of the religious life in a particular area.

I was curious about the county I grew up in, so I typed in my hometown zip code. For Chittenden County, Vermont, ARDA provides a bar graph showing the relative strength of mainline Protestants, evangelical Protestants and Catholics, as well as membership data for individual church bodies. I learned that evangelical Protestants (8,638) have almost matched mainline Protestants (9,427) in total numbers, though not surprisingly both are far outpaced by the Catholics (39,143).

The format also allows for fine-grained tracking of change over the decades, in percentages and actual numbers, for each religious group. In this case, the data show growth in evangelical and nondenominational churches and decline in United Church of Christ and United Methodist congregations. The report notes an even more dramatic figure: the number of religious adherents overall in Chittenden County has declined—from 57 percent of the population in 1980 to 39 percent in 2010. Those numbers tell a lot of what has happened to religious life in my hometown.