Milson Island is in the Hawkesbury towards the western shore and upstream of Peats Ferry Bridge. It was originally called Mud Island and named as such on Major Mitchell's map of 1834. This name presumably arose because of the extensive mud bank at the downstream end of the island which constituted a navigational hazard. It was an early land grant to an Aborigine called Granny Lewis and was brought by Robert Milson in 1865. It was purchased by the government in 1901. Robert Milson lived on the mainland between the island and Kangaroo Point; he died in 1886 and was buried on Bar Island. The current name appears on an Admiralty chart of 1872, and an 1898 Lands Department map shows the island as Milson or Mud Island.