Lands were acquired in 1973 "for use as an inviolate sanctuary...for migratory birds." The refuge lies within the floodplain of the Swan River above Swan Lake and between the Swan Mountain Range to the east and the Mission Mountain Range to the west. The valley was formed when glacial ice poured down the steep slopes of the Mission Range into Swan Lake. The valley floor is generally flat but rises steeply to adjacent forested mountain sides. 80% of the floodplain is composed of reed canary grass and the other 20% consists of forests of old growth fir, spruce, cedar and larch. Large cottonwood trees exist along the river. Swan River, which once meandered through the floodplain, has been forced to the west side of the refuge by deposits of silt, leaving a series of oxbow sloughs within the refuge floodplain. There are no significant developments or facilities on the refuge. Waterfowl species consist of Canada geese, mallards, cinnamon teal and common goldeneye. The refuge provides a nesting site for a pair of bald eagles.