Clayton is a Borough in Gloucester County, New Jersey, United States. As of the United States 2000 Census, the borough population was 7,139. What is now Clayton was originally formed as Clayton Township, which was created on February 5, 1858, from portions of Franklin Township. Portions of the township were taken to form Glassboro Township on March 11, 1878. Clayton was formed as a borough by an Act of the New Jersey Legislature on May 9, 1887, from portions of Clayton Township.