Mulberry Island was fortified by Confederates in 1862, then abandoned in the withdrawal from the Williamsburg line
Source: US Geological Survey, Vicinity of Fort Monroe, peninsula between York and James Rivers, Virginia (1910-1911, Sheet 2)
the French fleet had frigates in the James River at Mulberry Island in 1781, as it blocked General Cornwallis from escaping Yorktown
Source: Boston Public Library, Norman B. Leventhal Map & Education Center, A plan of the entrance of Chesapeak Bay, with James and York rivers... (1781)