I visited the Sharpsburg battlefield in 2012. I was amazed that the Dunker Church, Burnside’s Bridge and other features were still there and that corn was still being grown in the famous Corn Field.
The Dunker Church survived the battle and was repaired and reused for some time thereafter. Eventually the congregation moved and the building fell into disrepair, helped along by souvenir hunters. It collapsed in 1921. A house was later built on the original foundation. This became a gas station and eventually a souvenir shop. The site was finally purchased by a private conservancy group and donated to the NPS. The church that you see today is a reconstruction done for the centennial in 1962. There was plenty of documentary evidence for the original structure so the reconstruction is quite exact.