From the Guidebook:
discovered on the nearby surface of Searles Lake by John Searles in 1862. With his
brother Dennis, he formed the San Bernardino Borax Mining
Company in 1873 and operated it until 1897. The chemicals
in Searles Lake, which included borax, potash, soda ash, salt cake, and
lithium, were deposited here by the runoff waters from
melting ice age glaciers. John Searles' discovery has
proved to be the world's richest chemical storehouse,
containing half the natural elements known to man.
Plaque placed by the California State Park Commission in cooperation with the Death Valley 49ers, the American Potash & Chemical Corp. and the West End Chemical Division of Stauffer Chemical Corp. November 8, 1962.