A google search will show that even the State of Idaho [in its DNR and tourism pages] gave up on spelling the river consistently, where a search on Jarbidge comes up with a page where it is also spelled Jarbridge, as it is elsewhere at the [same] site. Seems the Jarbridge is one of the Jarbidge rivers.
Paul Gibson also surrendered on his own web page for the quilt, which makes sense, to help hangers find something he'd like to sell. Note a direct copy from his page, as found 17 months ago.
Jarbidge River Under Quilt
The Jarbridge River under quilt is designed to offer a more trim variation to our quilt designs. At 42" wide by 58" long it gives shoulder to shoulder and neck to ankle coverage for many folks. Weighing in at under 20oz's(3season) the Jarbridge is a great choice for those looking to save some weight over a full size quilt but still looking to make use of a small pad for their feet.
At HF, the Jarbridge UQ gets many more mentions that the Jarbidge. In Idaho, it is otherwise. And in Utah, it is overwhelming Jarbidge[, referring to the same river.]
Excuse me if this is an old joke Paul has covered as often as he has recently, sewn, threaded and packed UQ's referred to both ways.
Myself, I'm very happy....with a Lawst River UQ.