All of present-day Union County was part of the Elizabethtown Tract, which was purchased in 1664, by English colonists from the Lenape Native Americans that lived in the area of present-day Elizabeth, New Jersey. Union County was formed on March 19, 1857, from portions of Essex County; it was the last of New Jersey's 21 counties to be established.Many historic places and structures are to be found in the county, including on the National Register of Historic Places listings in Union County, New Jersey.Every fall, Union County holds its annual "Four Centuries in a Weekend" festival for the public, celebrating and touring historic buildings, museums, and sites in the county.
