Atglen is a borough in Chester County, Pennsylvania, United States. The population was 1,406 at the 2010 census.
The land upon which Atglen now stands was once a wilderness. Cutting through it were paths made by Indians who traveled from Paxtang (present day Harrisburg) to present day Newcastle, Delaware to trade with the Swedes and later, the English. In 1717, Sadsbury township was organized. It included all of present-day Sadsbury Township as well as Fallowfield, Highland, and Valley townships.In August 1728, several inhabitants petitioned the court to separate Sadsbury from Fallowfield because of the former's size.In November 1728, the township was subdivided into East and West Sadsbury, and in 1729, upon the division of Chester County into Lancaster and Chester counties, the line between the two divisions of the township was made to conform to the county line.The earliest settlers in the vicinity of Atglen appear to have been the Philips and the Moores. The former owning much of the valley upon which the borough of Atglen now stands, and the latter the hilly area north of the borough west to Nobleville, south of present-day Christiana.