Oak Island was an island off Britain, possibly what was once Land's End, as most of South-West England was turned into an archipelago (the 'Western Archipelago'). Raft Cities or amphibious Suburbs could not access it because of it's rocky shores and local defenses.
The island is rocky on it's coast, but behind these cliffs lies pretty woodland and small hills. It is possible the ground there is alkaline, as the ground in the South-West of England is mainly chalky, hence the 'White Cliffs of Dover'.
Sometime in the later Traction Era a small traction town got tired of being chased around by larger cities. So it went to the coast of the Great Hunting Ground, put itself on floats and 'swam' over to Oak Island, and set up as a static town. Later the traction town was known simply as Dunroamin', but it's unlikely it was called that while it was a traction city.
Hester escaped the attack via a fishing boat, suggesting that most or at least some of the food or trade on Oak Island came from the fishing industry there.
The island has had a long history of Anti-Tractionism since Dunroamin' settled down there. Hester had an Anti-Tractionist stance but didn't seem very loyal or devoted to the concept. This suggests the town was not part of the ATL, as the League would openly attack cities that provoked them too much.