"Congress has made it easier for unwed American mothers than it is for unwed fathers to pass on their citizenship. The foreign-born baby of an unmarried American mother is a U.S. citizen if the mother lived in the United States for at least one year."
http://articles.latimes.com/2010/nov/11/nation/la-na-court-citizenship-20101111
In 1961, it was 10 years residency, 5 after the age of 14. So, 19.