Blairstown is a Township in Warren County, New Jersey, United States. As of the 2010 United States Census, the township population was 5,967.
Blairstown Township 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. It is located in Warren County, New Jersey.
According to the United States Census Bureau, the township has a total area of 31.8 square miles (82.3 km²), of which, 31.0 square miles (80.3 km²) of it is land and 0.8 square miles (1.9 km²) of it (2.36%) is water. The township is located in the Kittatinny Valley which is a section of the 700 mile long Great Appalachian Valley that stretches from Canada to Alabama.