Rumson is a borough in Monmouth County, New Jersey, United States and is part of the New York Metropolitan Area. As of the 2010 census, the borough's population was 7,122, reflecting a decline of 15 from 7,137 in 2000, which had in turn increased by 436 from 6,701 in 1990.Rumson was formed by an act of the New Jersey Legislature on March 15, 1907, from portions of Shrewsbury Township, based on results of a referendum held on June 18, 1907.