Black and white lantern slide of Obsidian Cliff, Wyoming.

Black and white lantern slide close-up view of petrified trees in the grass with measuring sticks.

Black and white lantern slide of Audie Merrill posing on a hillside next to a fenced-in petrified tree. Two other people, Sinclair and Virginia, are visible through the fence.

Black and white photograph of a dirt road leading to a pyramid on the top of a mountain.

Black and white lantern slide of a slab of rocks near a beach. The label on the slide reads "The 'slab walk,' lower section."

Black and white lantern slide of the Liberty Cap rock formation in Yellowstone National Park.

Black and white lantern slide of seven people aboard a small boat, reading the meter of a water gauge in the Yellow River.

Black and white lantern slide of six people aboard a small boat, reading the meter of a water gauge in the Yellow River.

Black and white lantern slide of two men with a silt pump. One man holds a bucket under the pump spout.

Black and white lantern slide of two men standing at the bank of the Yellow River near a gauging station.

Black and white lantern slide of a natural bridge rock formation on an upper beach of Lake Yellowstone.

Black and white lantern slide of the Fish Pot hot spring in Yellowstone National Park.

Black and white lantern slide of Lena Merrill standing in front of a boulder in Yellowstone National Park.

Black and white lantern slide of Roaring Mountain in Yellowstone National Park.

Black and white lantern slide of rock formations at the Silver Gate site in Yellowstone National Park.

Black and white lantern slide copy of the Yellowstone Park Map from a 1939 guidebook.

Black and white lantern slide of a black bear cub.

Black and white lantern slide of a black bear cub.

Black and white lantern slide of the Golden Gate Viaduct in Yellowstone National Park.

Black and white lantern slide copy map of the Upper Geyser Basin of Yellowstone National Park from an unknown source.

Black and white lantern slide of Robert Merrill standing next to the Lone Star Geyser Cone in Yellowstone National Park.

Black and white lantern slide of the Old Faithful geyser in eruption taken from Observation Point in Yellowstone National Park.

Black and white lantern slide of the Yen Chow Fu spillway. A low brick wall separates spillways and a small building sits to the right of the frame.

Black and white lantern slide of the masonry walls of the Yen Chow Fu spillway.