Sharkey Hot Spring
Sharkey Hot Spring runs at 126 degrees Fahrenheit on BLM land in Lemhi County, just 286 feet from National Forest Development Road 185. Recent USGS sampling measured it even hotter at 146 degrees with a pH of 8.0 and sodium levels of 270 mg/L — among the highest sodium concentrations in Idaho's thermal springs.
The spring sits at 5,440 feet in the dry, open landscape near Salmon, where sagebrush and bunchgrass stretch across rolling hills. Annual precipitation is under 19 inches, giving the area a semi-arid character unusual for Idaho hot springs. Mineral deposits stain the ground near the source, and the sulfate-rich water carries a faint mineral smell. The Salmon River corridor opens to the west with wide valley views.
The spring is roadside, accessible by vehicle via NFDR 185. Water emerges dangerously hot at the source, so test carefully and look for any cooled pools downstream. Agency Creek Campground is about 8 km away along the Lewis and Clark National Backcountry Byway, with a 14-day stay limit. No reservations needed.
This section of Lemhi County lies along the Lemhi Range, where deep faults channel geothermal water to the surface. The water chemistry — high sodium, elevated sulfate, low calcium — points to prolonged contact with volcanic rock at depth. The BLM has maintained open access to the spring, which sits on public land managed through the Salmon Field Office.
The water at Sharkey Hot Spring is slightly alkaline (pH 8.0).
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Agency Creek Campground (4 campsites) is located along the Lewis and Clark National Backcountry Byway, near the Lewis and Clark National Historic Trail and the Continental Divide National Scenic Trail. At the top of the pass, there is a memorial to Sacajawea. This secluded, arid area offers a variety of recreation activities including camping, biking, hiking, hunting, OHV riding, picnicking and wildlife viewing. Please be respectful of cultural and historical items found here.
Sharkey Hot Spring sits at 5,440 feet above sea level, way above the mile-high mark. You may not feel the altitude strongly, but hot water still dehydrates you faster at elevation. UV is about 22% stronger than at sea level, so bring sunscreen and drink more water than you normally would.
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Sharkey Hot Spring is road-accessible, so you can bring more gear. The water runs hot, so extra hydration is key. Cold air temperatures make a changing robe or warm layers essential.
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