Antietam National Military Park is located near Sharpsburg, Maryland, right on the Potomac River, about an hour northwest of Washington D.C.  In the South this battle was referred to as Sharpsburg because the Confederacy normally named battles after the nearest town, whereas the North frequently named them after the nearest geographical feature, in this case Antietam Creek.  Antietam was significant because it was one of the few bright spots for the Union Army during the first year or two of the war.  Although it was considered a draw, the North successfully pushed Robert E. Lee's Army of Northern Virginia back across the Potomac, into the Confederacy.  It is also thought that if the South had been victorious at Antietam, the likelihood of European intervention on their behalf would have greatly increased.  Finally, President Lincoln, waiting for a victory, seized this opportunity to issue his Emancipation Proclamation which freed slaves in all of the Confederate states. 

Antietam might be one of the most interesting and easy to understand large scale Civil War battlefields to visit.  It's easier to understand than many other battlefields because rather than being a conflict that spanned multiple days, Antietam was fought on a single day, September 17, 1862.  Therefore, understanding the troop movements across the terrain is much easier, as there were only three major phases of the battle: the cornfield in the morning, Bloody Lane at midday, and Burnside Bridge in the afternoon.  What makes Antietam interesting are all of the landmarks, including the three just mentioned, as well as Dunker's Church.  Although it was only a one day battle, the number of recognizable landmarks on this battlefield are enough to get any Civil War buff's heart racing.  I cannot tell you how remarkable it was to stand in the cornfield, look down from an observation tower onto Bloody Lane, and walk across Burnside Bridge.  While walking the ground at Antietam, visitors feel the weight of the battle that took place there which resulted in 25,000 casualties, the bloodiest day of the Civil War.

The battlefield site is run by the National Park Service and includes a visitor's center which has exhibits and audiovisual programs.  Visitors can also pick up a brochure at the center with a map of the battlefield which will guide them through all of the major areas of the battle.  I was there in September and it was still extremely warm and humid; so if you go during the summer months be prepared for an oppressive, southern type of heat and humidity.  Here are some resources which will give you more information about the battle, as well as some information about visiting the site:

• The Insider's Guide to Civil War Sites in the Eastern Theater - This is an excellent book which not only gives information about the battlefield site, but also some sites which are located near the battlefield, in and around the town of Sharpsburg.
• A Tour Guide to the Civil War - This book gives a small piece of information about the battle, and is organized by state. 
• Guide to the Battle of Antietam - This is for people who want to know everything there is to know about the battle.  It gives almost moment by moment information based on the letters of those who were involved.