Amstel County, and Upland County, which was later partitioned between New Castle County, Delaware, and the Colony of Pennsylvania. The three counties were created on September 12, 1673, the first two on the west shore of the Delaware River and the third on both sides of the river. The Treaty of Westminster of 1674 ended the second period of Dutch control and required them to return all of New Netherland to the English on June 29, including the three counties which they created. After taking stock, the English declared on November 11 that settlements on the west side of the Delaware River and Delaware Bay were to be dependent on the Province of New York, including the three Counties. This declaration was followed by a declaration that renamed New Amstel as New Castle. The other counties retained their Dutch names. The next step in the assimilation of New Sweden into New York was the extension of the Duke's laws into the region on September 22, 1676. This was followed by the partition of some Upland Counties to conform to the borders of Pennsylvania and Delaware, with most of the Delaware portion going to New Castle County on November 12, 1678. The remainder of Upland continued in place under the same name. On June 21, 1680, New Castle and Hoarkill Counties were partitioned to produce St. Jones County. On March 4, 1681, what had been the colony of New Sweden was formally partitioned into the colonies of Delaware and Pennsylvania. The border was established 12 miles north of New Castle, and the northern limit of Pennsylvania was set at 42 degrees north latitude. The eastern limit was the border with New Jersey at the Delaware River, while the western limit was undefined. In June 1681, Upland ceased to exist as the result of the reorganization of the Colony of Pennsylvania, with the Upland government becoming the government of Chester County, Pennsylvania. On August 24, 1682, the Duke of York transferred the western Delaware River region to William Penn, including Delaware, thus transferring Deale County and St. Jones County from New York to Delaware. St. Jones County was renamed Kent County, Deale County was renamed Sussex County, and New Castle County retained its name. Swedish explorer and botanist Pehr Kalm visited the descendants of the early Swedish immigrants to New Sweden in the mid-18th century and documented their experiences with the Native