The value of all farms, rural land, hunting land and other land for sale in Union County recently was around $17 million, representing a combined 6,551 acres of land for sale in Union County. Union County ranks 20th in the Garden State based on the combined acreage of land for sale among all the counties in the Garden State. Of all farms, rural land, hunting land and other land for sale in Union County, Roselle Park had the most land for sale. Union County is New Jersey's 20th largest county (105 square miles). It's located in the North New Jersey region of New Jersey.