Allentown is a borough in Monmouth County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 1,828, reflecting a decline of 54 from the 1,882 counted in the 2000 Census, which had in turn increased by 54 from the 1,828 counted in the 1990 Census.Allentown was incorporated as a borough by an act of the New Jersey Legislature on January 29, 1889, from portions of Upper Freehold Township, based on the results of a referendum held that day. The borough was named for settler Robert Burnet's son-in-law, Nathan Allen or for William Allen, who served as Chief Justice of the Province of Pennsylvania.Allentown's shopping district has antique and specialty shops, as well as restaurants. Many historic homes and historic buildings are located in the borough. The Horse Park of New Jersey is a park located near the borough but does have an Allentown mailing address.