Hot Springs of Gardiner's River, Yellowstone

Those two tiny red-shirted figures on the left slope are the key to the whole picture. Without them, the stepped terraces of mineral rock in the center could be any size at all. With them, you realize you are looking at something enormous. This is Mammoth Hot Springs, where hot water loaded with dissolved limestone spills down the hillside and leaves behind travertine, building shelf after shelf over centuries. Thomas Moran painted the rust, ochre and pale blue of the mineral pools in thin washes of watercolor, letting the white of the paper do the work for the bleached stone.

Moran made his first trip to Yellowstone in 1871 as part of the Hayden Geological Survey, borrowing money to get there since he was not a wealthy man and had never spent much time on horseback. He came back with sketches and watercolors that were shown to members of Congress alongside William Henry Jackson's photographs. In March 1872, Yellowstone became the world's first national park. Moran signed his work with a monogram and later took to calling himself Thomas "Yellowstone" Moran, which tells you how much the place shaped his career. His style belongs to the Hudson River School tradition of grand American landscape, though in watercolor he worked looser and faster, more interested in the strange colors of the place than in polish.