After the surrender of a second British army at the Siege of Yorktown in 1781, Britain signed a peace treaty. American sovereignty became internationally recognized, and the new nation took possession of substantial territory east of the Mississippi River, from what is today Canada in the north and Florida in the south.As it became increasingly apparent that the Confederation was insufficient to govern the new country, nationalists advocated for and led the Philadelphia Convention of 1787 in writing the United States Constitution to replace it, ratified in state conventions in 1788.