|Confederate dead at the Bloody Lane, Sharpsburg, MD, 18 September 1862|
You can read about the battle at numerous places on the web. The National Park Service site is excellent; there's about a 20-minute animated run through of the battle here, and worth your time. And YouTube has a fine narrative if you want to settle in for 45 minutes of history lesson. Here it is:
We should take some sober time today to think about what these horrible events mean. Are we any closer to a more perfect union today? How? Are we any closer to realizing the futility of war? Why did these boys die?