St. Mary's Island was originally called 'Bates Island', 'Hartley Bates' or 'Bates Hill'.
Its name has some connection with the Bates family who were prominent in the area.
In medieval times there was a chapel on the little rock dedicated to St. Helen.
Within it was the Lady-light, also called St. Katherine's light
and by wrong ascription to St. Mary the island later received its second name.
The light was probably not burnt to warn shipping, but was purely religious.
Traces of St. Helen's Chapel were destroyed when the present lighthouse was built in 1898.
Attached to the lighthouse was a graveyard in which interment took place until 1680