Care by fathers was most common in the West and Midwest and least common in the South.
Care by married fathers with preschoolers whose mothers are employed is more common in some areas of the country than in others. In 2010, fathers in the West were the most likely to be taking care of their children and to be providing primary care, while those in the South were the least likely to be doing so. About 24 percent of fathers in the Midwest and West provided care for their preschoolers during the mothers' working hours, compared with 19 percent of fathers in the Northeast and only 15 percent in the South. Geographical differences in the frequency of fathers caring for their children may relate to regional variations in employment rates, and in costs of childcare and amounts of family income available to purchase alternative childcare services. Childcare costs are indeed more expensive in the Northeast than in the South. It could also be that childcare facilities may be farther away in some areas than in others; this might cause more people to choose neighbors and relatives (including fathers) over childcare facilities that may be less accessible.
Sources: Who's Minding the Kids? Child Care Arrangements: Spring 2010 (SIPP 2008)
http://www.census.gov/hhes/childcare/data/sipp/2010/tables.html
One-Third of Fathers with Working Wives Regularly Care for Their Children, Census Bureau Reports, CB11-198, Monday, December 5, 2011. http://www.census.gov/newsroom/releases/archives/children/cb11-198.html