The river was effectively created when Edward Southwell (1705–1755) landlord of Downpatrick built a tidal barrier at the Quoile and began draining the land, creating 500 acres of land from what was previously the western branch of Strangford Lough.

Harris, in 1744, mistakenly writes that the name of the bridge should be Coyne (after the branch of Loch Cuan up stream) not Coyle because he overlooked the origin.

On the north bank of the river, 0.75 miles (1.2 km) north-west of Downpatrick, the Inch Abbey site was originally on an island (Irish: Inis) in the Quoile Marshes.

However, the tides of Strangford Lough made time-keeping difficult and there was insufficient low-volume, high-value trade suitable for a steam-boat route.

[4] The iron steamship Robert Burns, 120 gross tons, built in 1857 on the Clyde, provided a regular cargo service from the Quoile to northern English ports for 17 years from 1866.