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. This small town has been the scene of many important moments over the centuries.  Here's the definitive account:

A Short History of Allentown, New Jersey

by John Fabiano et al.

Source: The Allentown Village Initiative
History of Allentown