Important dates in U. S. history By cadenhyle Jul 2, 1776 Declaration of Independence Jun 21, 1788 Constitution of the United States of America Apr 12, 1861 civil war started Apr 9, 1865 civil war ended Sep 1, 1939 ww2 start Dec 7, 1941 japanese attack on pearl harbor Sep 2, 1945 ww2 end Sep 24, 1945 united nations formed Dec 1, 1955 rosa parks Jul 2, 1964 civil rights act