The Dunker movement began in Germany in the early eighteenth century. The peace treaty that ended the Thirty Years War ( 1618 –1648 ) recognized three state churches. Dissenters were persecuted and forced to meet in communities where some degree of tolerance prevailed. In 1708 the denomination was formed with the baptism of eight believers by full immersion. The name Dunker derives from this method of baptism. However they were more commonly known as the German Baptist Brethren. In 1908 the official name became Church of the Brethren.

Because of the church's prominence in the Battle of Antietam, many believe that the Dunkers were the dominant religious denomination in the Sharpsburg area. Actually, they were a very visible, yet prominent minority. The original settlers to this region in the mid 18th century, were the so called "Pennsylvania Germans" or "Deutsche" (Pennsylvania Dutch). These people arrived in the early 1700's and settled in southeastern and south central Pennsylvania before moving into western Maryland and the Shenandoah Valley of Virginia.

One misnomer concerning the Germans is that they were all "Plain People" or "Sect People" (Members of the Dunker, Mennonite or Amish sects). While it is true that the first sizable influx of Germans were Mennonites, these so-called "Sect People" were a minority. The large majority, as many as 90 percent, of the Germans that came to the New World were known as the "Church People," members of the Lutheran and Reformed Church. So it was with the citizens of Sharpsburg and the surrounding countryside. Thus, while some noted area families such as the Mummas were Dunkers, most of the other farm families were not.

Dunkers practiced modesty in their dress and general lifestyle. Other Christian principles which the Dunker's stress are: pacifism, members both North and South refused military service; the brotherhood of man, including opposition to slavery; and temperance, total abstinence from alcohol. A typical Dunker church service supported their beliefs in simplicity. Hymns were sung with no musical accompaniment from organ, piano or other instruments. The congregation was divided with men seated on one side and women on the other. The churches were simple with no stained glass windows, steeple or crosses.

The Mumma Bible

Daniel Miller who owned the famous "Cornfield," donated the leather bound volume to the Dunker congregation in 1853. A short time after the Battle of Antietam Sergeant Nathan Dykeman, Company H, 107th New York, took the bible. It remained in his home in Schuyler County, New York until his death in 1903. Dykeman's sister decided to return the bible to its rightful owners and sold it to the veterans organization of the 107th New York. They in turn gave it to Mr. John T. Lewis, an African –American who had migrated to New York in 1862 from his native Carroll County, Maryland. Lewis was a convert to the Brethren Church and returned the bible to the Sharpsburg congregation in 1903. Later, the bible came into the possession of several church members for safekeeping. It eventually was acquired by the Washington County Historical Society and donated to the National Park Service. Today the Mumma Bible is on display in the museum of the Antietam National Battlefield.