U.S. History 1775-1800 By maherja Jul 8, 1783 The Supreme Court of Massachusetts abolishes slavery in that state. May 25, 1787 Constitutional Convention meets in Philadelphia Sep 29, 1789 The U.S. Army is established by Congress. Jun 1, 1792 Kentucky becomes the 15th state. Jun 1, 1796 Tennessee becomes the 16th state