 Delaware changed hands between the Dutch and Swedes between 1631 and <unk> . The Dutch maintained control of Delaware until 1664 , when Sir Robert Carr took New <unk> for the Duke of York , renaming it New Castle . A Deputy of the Duke governed Delaware from 1664 to 1682 . When William Penn received his land grant of Pennsylvania in 1681 , he received the Delaware area from the Duke of York , and dubbed them " The Three Lower Counties on the Delaware River " . In 1701 , after he had troubles governing the ethnically diverse Delaware territory , Penn agreed to allow them a separate colonial assembly . 
