The Dunker Church is one of the most iconic structures of the American Civil War. Surprisingly, few people know much if anything about its fascinating story or the role it played within the community of Sharpsburg and its importance during and after the Battle of Antietam. September Mourn: The Dunker Church of Antietam by Alann D. Schmidt and Terry W. Barkley rectifies this oversight in the first book-length study of its kind. On September 17, 1862, two mighty armies grappled across the rolling hills, fields, and woodlots surrounding Sharpsburg, Maryland. The combat left more than 23,000 Union and Confederate soldiers killed, wounded, or captured, repulsed Lee's invading Virginia army, and paved the way for the Emancipation Proclamation. Ironically, in the epicenter of that bloodiest day in American history stood a small whitewashed building dedicated to peace, equality, and the brotherhood of man. The German Baptist Brethren, or Dunkers (Dunkards) as they were colloquially known, built the Mumma Church of the Manor congregation in 1853 just nine years before Antietam. In addition to being a house of worship with important ties to the local community, the history of the Dunker Church is interwoven with such notable figures as Stonewall Jackson, Clara Barton, Abraham Lincoln, and even Mark Twain. The structure was heavily damaged during the battle, housed torn bodies as a hospital in its aftermath, and suffered a complete collapse before undergoing the long and arduous process of being rebuilt. Schmidt's and Barkley's impressive September Mourn is based upon years of meticulous research from both a Church of the Brethren (Dunkers) and a National Park Service perspective. The authors establish the importance of the structure to Sharpsburg and its citizens, its role during the battle and its aftermath, and how it helped establish tourism and education for future generations of Americans. The Dunker Church can finally take its place alongside the Alamo and Shiloh churches as one of the most notable houses of worship in American military history. September Mourn: The Dunker Church of Antietam is a must-read for anyone interested in the full story of the monumental battle and the community who lived through it.