"The nation’s prisons held approximately 744,200 fathers and 65,600 mothers at midyear 2007 (appendix table 1). Fathers in prison reported having 1,559,200 children; mothers reported 147,400."

Source

Glaze, Lauren E., and Maruschak, Laura M., "Parents in Prison and Their Minor Children" (Washington, DC: US Dept. of Justice Bureau of Justice Statistics, Aug. 2008), NCJ222984, p. 2.
http://www.bjs.gov/content/pu…