Shewolf, the actual casualties on Omaha beach for D-Day, were estimated at around 2000, but the Cemetery above Omaha beach also contains the US Troops that were killed on Utah, the paratroopers who landed, but were killed inland, and others that were killed over the coming week of fierce fighting, as the Allies established a foothold on French territory.
Omaha is not the only US Cemetery, as there is also another in Brittany (called St James's)
http://www.ddaymuseum.co.uk/faq.htm
D-DAY......
"The breakdown of US casualties was 1465 dead, 3184 wounded, 1928 missing and 26 captured. Of the total US figure, 2499 casualties were from the US airborne troops (238 of them being deaths). The casualties at Utah Beach were relatively light: 197, including 60 missing. However, the US 1st and 29th Divisions together suffered around 2000 casualties at Omaha Beach."