Monmouth County is a county located on the coast of central New Jersey, in the United States within the New York metropolitan area, situated along the northern half of the Jersey Shore. As of the 2020 United States Census, Monmouth County's population was enumerated at 643,615, making it the state's fifth-most populous county, representing an increase of 13,245 from the 2010 Census, when the population was counted to be 630,380, in turn an increase of 15,079 from 615,301 at the 2000 Census.