Leads to Castle Hill, named after a fortified Siwanoy village on a hill.
Accounts differ on who gave the name. One NYC Parks page credits Adriaen Block, a 17th-century explorer for the New Netherland Company, who thought the fortified village resembled a castle; another says English settlers named the peninsula after the village, which overlooked the East River. According to NYC Parks, the avenue began as a Siwanoy path used as early as 700 A.D.