By an act approved on March 19, 1857, which become effective on April 13 of that year, the New Jersey State Legislature created “a separate county, to be called the county of Union.” This was the last of the state’s 21 counties to be established. 

The act passed the General Assembly by a vote of 43 to 10, the largest majority ever given to the establishment of a new county. But it had been a long struggle.

The story has its origin in the early days of settlement. In 1683 the provincial Assembly, meeting in Elizabethtown (Elizabeth), divided the province of East New Jersey into four counties: Bergen, Essex, Middlesex, and Monmouth. The area that is present-day Union County was included in Essex, where it would remain for almost 175 years.