Joseph Cooper began building a mill on Culeenup Island near the mouths of the Murray and Serpentine Rivers in 1843, to grind wheat for Pinjarra and Coolup farmers. It was first powered by large sails then converted to steam in the 1860’s
Early last century the Mill became a ruin. It was first restored in 1927 and became a popular picnic spot for boaters. Further restorations have occurred since the 1980’s. A caretaker has been installed and the jetty upgraded. In 1996 Cooper’s Mill was registered on the State Register of Heritage Places.
"Cooper’s Mill is only accessible by boat and is situated on the extreme north western end of Cooleenup Island, part of the Murray Delta where it enters the Peel Inlet. The walls were made of limestone blocks and the floor was limestone rubble. The roof was a shingle roof which rotated. It remains the earliest and the only remaining mill of its kind in the area.
The location may seem remote, but at that time it was well placed for early settlers on the river who took the shortest path by boat or bullock through the shallow water. Joseph Cooper began building the mill in the 1840s but died before he could see its completion. As a wheelwright he had the skills to make the machinery and had completed the mechanical parts before he died. His sons Thomas and James inherited the mill and with the help of Dan Myerick, a carpenter, and Josiah Stinton it was completed.
Research has shown that the difficulty faced by Joseph Cooper was enormous; stone probably came from a place 15km away, he would have rowed along a shallow pathway and it would have been a difficult place to unload. Accounts suggest that he used the easterly wind in the morning to row across and the sea breeze in the afternoon to return.
The mill was in use by 1850 and operated until 1865. Originally it was powered by the wind and then it was converted to steam. The mill was very important to wheat farmers who would otherwise have to mill by hand. When the mill was converted to steam its efficiency improved again, but the mill was becoming unviable as improvements in road transport, bridge building and farming north of Pinjarra took effect. When it closed down the equipment was sold to John Fawcett and it became a smokehouse for fishermen. Local people also made use of the limestone for chimneys." 
 Museum Without Walls mandurahcommunitymuseum.org