The Cooper River flows through the Cascade Mountain Range and has steep slopes associated with some of its shorelines.

While mining in the area surrounding Cooper Lake and damming Cle Elum River impacted the quality of the salmon habitat, salmon spawning has been prominent on Cle Elum River since the late 2000s.

[8]: 4-5  Shoreline access is found on the US Forest Service campground, motorboats are prohibited by county ordinance.

[5] Discovery of a Clovis point projectile along the bottom of Cle Elum Reservoir in 1984 leads to suggestions that the region may have been a site of the residence of Indigenous peoples of the Northwest Plateau with Clovis culture,[6]: 4-39, 4-40  perhaps of the Wenatchi People, one of the Confederated Tribes of the Colville Reservation and within the ceded lands of the Yakama Nation.

Archaeological surveying in the area shows no additional evidence from materials or engineering to confirm the discovery.

In the vicinity of the Salmon La Sac region lie prehistoric and early historic Native American sites including artifact scatter, petroglyphs, resource procurement areas, and seasonal salmon camps indicating that these may be associated with the Kittitas or other Bands and Tribes of the Yakama Nation.