The reservoir and adjacent community were named for early settler Ruth McKnight.

The reservoir was formed by construction of R. W. Matthews Dam in 1962 (63 years ago) (1962) primarily for domestic and industrial water supply to Arcata, Eureka, and other communities around Humboldt Bay.

[3] Dry-weather releases flow down the Mad River from the reservoir to be recovered by Humboldt Bay Municipal Water District's Ranney collectors near Essex, California.

[5] Registration and inspection is required for all watercraft prior to launching on Ruth Lake.

Trailered and motorized boats may be launched only at the marina or at the Ruth Recreational Campground.