"An estimated 809,800 prisoners of the 1,518,535 held in the nation's prisons at midyear 2007 were parents of minor children, or children under age 18. Parents held in the nation's prisons -- 52% of state inmates and 63% of federal inmates -- reported having an estimated 1,706,600 minor children, accounting for 2.3% of the U.S. resident population under age 18."

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. 1.
http://www.bjs.gov/content/pu…