We use data from a new longitudinal survey “the Fragile Families and Child Wellbeing Study" to examine how welfare and child support policies, and local labor market conditions, affect union formation among unmarried parents who have just had a child together. We use multinomial logistic regression to estimate the effects of the policy variables along with economic, cultural/interpersonal, and other factors on whether (relative to being in a cohabiting relationship) parents are not romantically involved, romantically involved living apart, or married to each other about one year after the child's birth. We find that "contrary to some previous research" higher welfare benefits discourage couples from breaking up, while strong child support enforcement reduces the chances that unmarried parents will marry; local unemployment rates do not appear to be strongly associated with union formation decisions after a nonmarital birth.