This man is standing next to Pelton Water Wheel, located inside the wood cover. Lester Allan Pelton invented the Pelton Water Wheel in the 1870s. In 1860, while living in Comptinville, a gold mining community, he designed an efficient energy source that was able to turn water into power.
Figure from Lester Allan Pelton's original October 1880 patent
Mammoth Bar was a mining community located on the Middle Fork of The American River.