New Castle County, Delaware On November 6, 1674, New Amstel was made dependent on New York Colony, and was renamed New Castle on November 11, 1674. On September 22, 1676, New Castle County was formally placed under the Duke of York's laws. It gained land from Upland County on November 12, 1678. On June 21, 1680, St. Jones County was carved from New Castle County. It is known today as Kent County, Delaware. On August 24, 1682, New Castle County, along with the rest of the surrounding land, was transferred from the Colony of New York to the possession of William Penn, who established
New Castle County, Delaware parallel. According to the U.S. Census Bureau, the county has a total area of , of which is land and (13.8%) is water. The boundaries of New Castle County are described in § 102 of the Delaware Code. The county is drained by Brandywine Creek, Christina River, and other channels. Its eastern edge sits along the Delaware River and Delaware Bay. Two small exclaves of the county and the state lie across the Delaware River, on its east bank on the New Jersey side, Finns Point adjacent to Pennsville Township, New Jersey, and the northern tip of Artificial Island, adjacent