Union County Administrative Offices are located in the Elizabethtown Plaza, Elizabeth NJ 07207; phone: 908‑527‑4100.
In the historic Elizabethtown Purchase of 1664, the Lenni Lenape Indians (sometimes referred to as the Delaware Indians) gave a group of English settlers title to an immense tract of land that extended from the Raritan to the Passaic Rivers, and westward for over thirty miles. (It is interesting to note that the Indians believed they were selling the rights to use the land for hunting, fishing, farming and such. The English concept of "owning" land was unknown to them at that time.) The purchase led to the first permanent English settlement in New Jersey. Elizabethtown was laid out along the Elizabeth River near the present Union County Courthouse. As the port of entry and first seat of New Jersey government, Elizabeth became a prominent and thriving economic center, and the leading settlement in the state.
In 1683, the General Assembly, meeting in Elizabethtown, divided East New Jersey into four counties: Bergen, Essex, Middlesex and Monmouth. What we know as Union County was originally a part of Essex County.
With the growth in population and continuous division and sale of land parcels, Elizabethtown's boundary lines continued to expand and divide. State legislature created the towns of Springfield (1793), Westfield (1794), Rahway (1804), Union (1808) and New Providence (1809).
Union County was officially formed by state legislature on March 19th, 1857. It was the last of New Jersey's counties to be created.