During the 1920’s South Plainfield, which was still a part of Piscataway Township, began to acquire an identity of its own. The area known as New Brooklyn became the center of town.
In 1924, an airport was built on John Hadley’s farm mainly for the use of the U.S. Postal Service. The first night airmail flight took off on July 1, 1925 and it took only 33 ½ hours to fly coast to coast. There were Sunday afternoon air shows announced by a young man who later became Mayor Henry Apgar. Bendix Aviation experimental planes and helicopters were tested at Hadley Airport.
After receiving permission from Piscataway Township and the State of New Jersey, South Plainfield was officially incorporated on March 12, 1926.
During the 1930’s most residents managed to survive as farmers, day laborers or W.P.A. workers who were paid by the federal government to build roads, bridges and sewers. People did what they had to in order to survive. They repaired their shoes over and over, made clothes from feed sacks, raised chickens and cows, planted their own gardens and ate wild fruit and nuts for food. Maple Avenue became a walkway for the women to bring the family cow to grazing land.
South Plainfield’s prosperity began in 1936 when Cornell-Dublier moved into the Spicer Building More than half of South Plainfield’s families were employed by Cornell-Dublier which manufactured condensers for the exploding radio industry. The site was chosen because of its frontage on the railroad line.
South Plainfield’s suburban character was established after World War II when the Geary Farm on Plainfield Avenue was developed into what became known as Geary Park. Shortly thereafter various housing developments sprang up throughout the north side of the Borough increasing South Plainfield’s population form 8,000 in 1959 to 18,000 in 1960.
Commercial and Industrial uses were attracted to the borough in the 1960’s and 70’s. The highlights were the construction of the Golden Acres Shopping Center, the Middlesex Mall and the Prudential Building. In the bicentennial year of 1976, South Plainfield’s population was 23,000. It remains at approximately that number today.