What was the largest battle ever fought in the history of the western hemisphere?

The largest battle ever fought in the history of the western hemisphere was the Battle of Gettysburg, a part of the American Civil War in July 1863. It lasted from the 1st to the 3rd of July. Estimates put the total number of troops engaged in fighting at around 160,000 (85,000 Federal and 75,000 Confederate).

The Battle of Gettysburg was the climax of a vast, evolving campaign in the eastern part of North America. The second day of the battle was the most murderous: approximately 20,000 soldiers were killed or went missing. 9 general officers of 120 died during the battle, no other battle claimed as many generals.

A lot of battlefield places were nameless before the Battle of Gettysburg and got their names right after it. Nowadays they are very popular among tourists.