I think it was the Battle of Bull Run in Manassas, VA in July 1861.

I visited the Civil War battleground of Stones River at Murfreesboro, TN. As I walked across those huge boulders and saw rusty metal wheels and cannons lying in place amid the huge rocks, that battle became a reality. I even saw buttons from the soldiers uniforms still lying where they had fallen onto the rocks; cannot figure out how they managed to still be stuck in the indentations on the rocks. I wonder how on earth they fought in places where feet could get caught between rocks breaking legs and that is the place where some of the caissons and cannons lie. The museum has lots of interesting things like uniforms with bullet holes, ammunition casings, guns, etc. Stones River Battleground is a very sobering place and one can't help but feel a reverence for the soldiers and all they had to go through.