Blairstown, New Jersey

Blairstown is a township in Warren County, in the U.S. state of New Jersey. As of the 2020 United States census, the township's population was 5,704, a decrease of 263 (−4.4%) from the 2010 census count of 5,967, which in turn reflected an increase of 220 (+3.8%) from the 5,747 counted in the 2000 census.

The area had been known as Smith's Mill and was later called Butts Bridge (variously spelled as "Butt's Bridge" and "Butts' Bridge"), named for a family that owned the eponymous crossing of the Paulins Kill.

Blairstown was incorporated as a township by an act of the New Jersey Legislature on April 14, 1845, from portions of Knowlton Township, based on the results of a referendum held that day. The township was named for John Insley Blair.