The original tree was a red river gum (Eucalyptus camaldulensis). Children of the first settlers played on this tree, dubbing it "Temple Bar", and fresh water was obtained from wells nearby. Early settlers including the Gougers, Everards and Thomases built tents and bush huts nearby.
In 1857 John Hector of the Savings Bank of South Australia conveyed the plot of land on which this gum tree stands to the Corporation of Glenelg. This was to commemorate the arrival of Governor Hindmarsh and subsequent reading of the proclamation nearby.
In 1963 the Old Gum Tree was repaired in plastic and cement due to deterioration. Two 18 pound short-range carronades from HMS "Buffalo", the ship in which Governor Hindmarsh traveled to South Australia, stand by the fence on the western edge of the reserve.