I was a little surprised to remember that South Dakota is where the first solar neutrinos were detected, in the old Homestake mine in Lead.
The detector was basically a huge container of dry cleaning fluid buried nearly a mile underground in an abandoned gold mine. The thick shield of rock was intended to prevent cosmic rays from producing false positives. But the weakly interactive neutrinos would pass unimpeded through the same mass, and theoretically cleave a chlorine atom from the perchloroethylene into a radioactive argon isotope.
It worked. It produced the first concrete evidence of the existence of the long theorized neutrino, a nearly massless particle that travels at the speed of light with virtually no interaction with the matter is passes through. Pretty cool. Of course, it's easy to overlook something when it's taking place a mile beneath the earth.