"One prime example is Antietam, or Sharpsburg. In a single day battle, from just before dawn to after dark on a long summer day, a combined 26,134 men were killed."
Estimates are 22,720 total casualties, of which 3,650 were killed, 17,300 wounded, and 1,770 missing/captured. You can verify my numbers at:
http://www.nps.gov/anti/casualty.htm
I realized my mistake of the totals after I posted. I knew the number was for killed and wounded, I just goofed on that one. Thanks.