North Springs
Inside Fish Springs National Wildlife Refuge, in Millard County, Utah, North Springs is one of several. Nothing is nearby. Delta, the closest town anyone recorded, sits almost sixty miles off. The water comes out warm, about what a tepid bath feels like. Access is restricted, and the ground is a National Wildlife Refuge held by the federal Fish and Wildlife Service.
The spring is almost on top of the road, fifteen feet off, inside the refuge. This is low desert, a bit over 4,300 feet, and very dry: around seven inches of rain a year and little snow. The refuge is federal land with a wildlife designation, so the rules are the refuge's rules.
Restricted access is the headline. Do not plan on soaking; plan on checking with the refuge before you go and following what they allow. Winter months are the best listed, and the dry climate makes that a reasonable window for the drive. No campground is on file. The water is mineral-heavy, sampled in 1990 with iron present.
The water at North Springs is slightly alkaline (pH 7.9) with 2910 mg/L total dissolved solids. It is notably rich in calcium (may support bone density and joint health), magnesium (known for muscle relaxation and stress relief), and sodium (supports circulation and skin hydration).