Estwatch is a small island not technically under any jurisdiction but desired by many nations and city-states for its strategic position. During the Dragon Age it is under the control of the Felicisima Armada which turned it into a notoriously lawless port.
At approximately -880 Ancient the Tevinter Imperium first settled the island. The Imperium fortified the largest natural bay on the island with a defensive wall and used the island as a facility to repair warships during military campaigns and slaving ventures against the Alamarri.
The time until the First Blight saw heavy usage of the island but the turmoil in the Imperium during this period halted Imperial naval activity in the Waking Sea. The island was essentially abandoned until Andraste's armies reached the island in -180 Ancient.
During the Divine and Glory Ages, the island remained unoccupied and the emptiness coupled with the debris from shipwrecks that littered the coast bred in the Free Marches the belief that the island was haunted or cursed, and contributed to the failure of any Marcher state to claim a lasting foothold on the land.
Estwatch became a naval base during the Storm Age. In 7:54 Storm the Qunari took the island as a base of operations in their war against the Free March states, Nevarra, and Orlais. During the Exalted Marches it was a site of heavy combat. In 7:78 Storm the Qunari lost the island to the Felicisima Armada with the aid of the New Exalted Marches. Raiders have since taken the port and the town of Little Llomerryn was built there as a nod to nearby Llomerryn.
See also EditCodex entry: The Raiders of the Waking Sea