South Plainfield is a borough in northern Middlesex County, in the U.S. state of New Jersey. The borough is situated on the border with Union County in the Raritan Valley region, within the New York metropolitan area.
South Plainfield’s landscape was formed thousands of years ago by a glacier. As the Glacier inched across the borough from the direction of New Durham Avenue towards Woodland Avenue it picked up soil along the way. As a result, the two highest points in the town are where the glacier started (Durham Avenue near what is now the Prudential/Motorola building) and where it began to melt (Woodland Avenue near the West Nine Golf Course). In the middle, a flat basin was formed near what is now Spring Lake. This delivered all the good topsoil to the north side of town – the soil content on the south side is shale. The landscape became important as prehistoric hunters arrived on the scene. They used the high points near Woodland Avenue and Durham Avenue as lookouts for the animals that grazed in the lower areas of town.
The area that later became South Plainfield was included in the “Elizabethtown Purchase” of 1664 as a part of Piscataway Township. The name “Piscataway” came from the “Piscataqua” Indians of Maine.
Logging was a significant industry of the time and a major operation was established along the Cedar Brook where a sawmill and gristmill were started in 1732.
Two hamlets developed in the mid-1700s. “Sampton” was located at the junction of what is now Sampton and Clinton Avenues, which was the main road from Elizabeth to New Brunswick. In the late 1700s, a tavern was established to serve travelers at what is now 746 Sampton Avenue. The second hamlet was called “Brooklyn” and it was located at Front Street and South Plainfield Avenue.