Battle of Antietam, September 17, 1862: 6 to 6:20 A.M.
Antietam Battlefield Board.
<a rel="nofollow" class="external text" href="https://www.loc.gov/item/map05000006/">Library of Congress: <i>Atlas of the battlefield of Antietam</i></a>, Washington, Govt. Print. Off., 1904.