It stands on a terrace in front of which a series of fish pens could be formed by fixing hurdles into a stone pavement. Next to these was a fish ladder, above which a great stone weir spanned the river. All this was built to take advantage of the plentiful salmon for which the Esk is well known. It seems possible that the coops were in fact holding pens for full-grown fish caught in the river, or breeding pens for raising small fish or fry.
The weir above the coops was first built in 1770 by Rev Dr Robert Graham, the owner of Netherby Hall and combined squire and parson ("Squarson") of Arthuret. Over his 25 years of ownership he carried out a long series of much-praised improvements to his estate, including the building of farmhouses and schools, and his establishment of the salmon fishery was a major part of this. But only a year after its construction floods swept the weir away. It was rebuilt and a second time destroyed in the same way. Brindley, the well-known civil engineer, rebuilt it yet again to an improved design incorporating a curved weir instead of a straight one. In 1782 this too collapsed when a huge weight of melting ice piled against it after a hard winter.
We do not know exactly when the Coop House was built - possibly in 1772 - nor do we know the name of its designer, nor even the reasons for its construction. Certainly it was an ornament to Dr Graham’s fine pleasure grounds, and it would have made a vantage point for watching the salmon fishery, for enjoying the sight of water cascading over the weir and fish leaping in the opposite direction. It may also have provided a shelter above the coops for a bailiff to keep watch for poachers.
As first built, the Coop House was little more than a belvedere of one room, its projecting bay taking full advantage of the view up and down the river. There was no fireplace, and it was entered directly from outside, through the arched south door. Each turret had a tall room on the ground floor, with a smaller space above. That on the west had an unlit basement room as well. Curiously, on the ground floor, the south and west windows of the west turret, and all three windows of the little room above, were blocked from the beginning.
With the failure of the weir, much of the point of the house would have been lost. It might still have come in useful as a base for fishing expeditions, or for the river bailiff, and even for the occasional picnic. But from the late 1780s it probably stood empty for most of the next 100 years or so. It was then turned into a cottage for estate workers. A range was installed under the middle window of the main room, which was then blocked. Bedrooms were made in the turrets, with pitched roofs that cut across the front and back windows; the ones in the east turret were therefore blocked up, as those in the west turret had always been, and new windows were made on the side overlooking the river. On the other side an extra room was added in front of the old main door, and a new front door was made in the east side of this addition.
In the 1930s the cottage was lived in by a shepherd, his wife and their five children, but it became too small for them and they moved to a larger house. After they left the Coop House remained empty becoming increasingly ruinous as the years went by.