Robinson Bar Hot Springs
Robinson Bar Hot Springs reaches 131 degrees Fahrenheit at 5,960 feet along National Forest Development Road 454 in Custer County. The water runs 90 degrees above the ambient air temperature, one of the largest thermal differentials among Idaho's roadside springs, with a TDS of 294 mg/L and iron content of 80 micrograms per liter.
The Yankee Fork of the Salmon River defines this landscape, a narrow, forested valley flanked by steep mountains in the heart of the Sawtooth Range. The spring surfaces just 230 feet from the gravel road, its outflow staining nearby rocks with iron deposits. Lodgepole pine and spruce dominate the surrounding forest. Winters are long and cold here, with over 10 feet of annual snowfall and average temperatures hovering around 41 degrees.
Robinson Bar takes its name from a historic river crossing and ranch site along the Yankee Fork, a drainage famous for 1870s gold dredging. The spring's chemistry, with 74 mg/L sodium, 50 mg/L sulfate, and 15 mg/L chloride, reflects deep circulation through the batholith before the water surfaces. Trace iron at 80 micrograms per liter accounts for the orange and rust-colored mineral staining visible near the source.
The spring is roadside via NF Road 454, though the road itself is remote and seasonal. Pole Flat Campground sits about 4.5 miles away with vault toilets, drinking water, and sites accommodating trailers up to 32 feet. The source water is dangerously hot and must cool before any contact. Access roads typically close from late fall through early summer depending on snowpack.
Is Robinson Bar Hot Springs worth visiting?
Best for
- Hot spring soaking
- Easy day trips
- Overnight camping trips
The water at Robinson Bar Hot Springs is alkaline (pH 9.4) with 294 mg/L total dissolved solids.
This campground is away from the main road and up the hill overlooking the river and the dredge ponds. Campsites include picnic tables tent pads fire rings with cooking grills. Campground amenities include a vault toilet and drinking water. Sites accommodate trailers and motorhomes up to 32 feet long.