We've heard these stats before: lower education levels, income, and age are all correlated to higher rates of single mothers. A U.S. Census report released today suggests geography may play a role as well.
The report [PDF] analyzes 2011 American Community Survey data, and charts the percentage of women (between the ages of 15 and 50) who had babies between January 2010 and December 2011 who were also unmarried. The metropolitan areas in the map below are color-coded based on their deviation from the norm (35.7 percent of new mothers nationally). Purple metros have "significantly higher" rates of unwed new mothers than the national average and green have "significantly lower."
Flagstaff, Arizona had the highest share of new mothers that were unmarried (74.6 percent) and Cheyenne, Wyoming had the lowest (4.7 percent). (Complete results are available here.) There are of course a few caveats that the Census points out. First of all, having a baby during that particular timeframe is a "relatively rare event" and the data "can be quite variable," so the margins of error on these rate estimates are fairly high and the differences between some metros, say Flagstaff and Greenville, North Carolina at 69.4 percent, is not statistically different. Also, the survey asked if women were unmarried at the time of the survey, not at the time of the birth, and also tracked where the mother was living then as well, not where she had her child.