What was the deadliest battle in American history?

There are many deadliest wars occurred in America, there is a great history of wars of America but the most deadliest war of America is American civil war. This war has changed the America. There was two parts of America one was southern and other was northern. The Northern America was well established and the industry was growing well in northern but on the southern side people were subjected to slavery. Thats why the war occured between the united states' of America and federate states of America between 1861-1865 and was the deadliest.