The village of Allen developed in the 18th century at the headwaters of Wicomico Creek around the grist mill established by John Adams, a son of the Rev. Alexander Adams (rector of Stepney Parish from 1704 to 1769). The milldam formed Passerdyke Pond, still a village landmark, and the spillway or trap gave the settlement its first name, the Trap, later becoming Upper Trappe, to distinguish it from a village of the same name in Worcester County.

The name was not changed to Allen until 1884, when it was named after Joseph S. C. Allen, the first postmaster. In the late 18th century the village had a tavern, a store and a sawmill, in addition to the gristmill. The waterfront of Passerdyke Creek thrived with commerce in the 19th century. The Methodist Church was established in 1829, and by 1860 there was a post office in the village. Several general stores have operated in the village duriing its history.

Much of the village we see today lies on two colonial land patents, "Monsham" , patented by John Christopher in 1683 and "Dashiell's Lott", patented by Col. George Dashiell in 1721, being a resurvey of the "Bennett's Adventure" patented in 1665 to Major Richard Bennett, formerly a Governor of the Virginia Colony.

Map numbers correspond to site numbers listed above