From the Wikipedia page 
Whitefield House and Gray Cottage, also known the Ephrata Tract, are two historic homes located at Nazareth, Northampton County, Pennsylvania. They were both built about 1740, by Moravian settlers who moved to Nazareth after the failure of their mission to Native Americans and Europeans in the Savannah, Georgia area, 1735-1740. The Whitefield House, also known as the Ephrata House, is a stone building measuring 56 feet long and 35 feet wide. It is named for George Whitefield (1714-1770). The Gray Cottage is a 1 1/2 story log building with a wood shake covered gable roof. It was completely restored in 1971, and is the oldest American Moravian building still standing.
The Moravian Historical Society website is  (checked November 2017)