Peapack-Gladstone (also written as Peapack and Gladstone) is a borough in Somerset County in the U.S. state of New Jersey. As of the 2010 Census, the borough's population was 2,582, reflecting an increase of 149 (+6.1%) from the 2,433 counted in the 2000 Census, which had in turn increased by 322 (+15.3%) from the 2,111 counted in the 1990 Census.