The United States equivalent of the Latin American free womb laws. Under the provisions of these laws, slaves born after a certain date would be freed on their 21st birthday. Slaves born before that date would remain slaves for life. The first such law was passed in Pennsylvania in 1780. Other northern states with large slave populations followed suit with similar post-nati laws. But as in Latin America, the passage of these laws led to such agitation among slaves born before the prescribed date and northern abolitionists that the states found they had to quickly pass a law calling for general manumission by a specific date. In some cases, slaves were freed much sooner than they would have been under the post-nati laws.