O’Sullivan was part of a group of critically acclaimed 19th-century photographers — A.J. Russell, J.K. Hillers and William Bell — who went West in the 1860s and 1870s.
O’Sullivan was a photographer for two ambitious geographical surveys. He accompanied geologist Clarence King on the Geologic and Geographic Survey of the Fortieth Parallel and Lt. George M. Wheeler on the Geographical and Geological Surveys West of the 100th Meridian. During seven seasons (1867-1874) traversing the mountain and desert regions of the Western U.S., he created influential visual accounts of the American interior.
O’Sullivan first saw Shoshone Falls in September 1868 and it is the only site in the American interior he photographed twice during all his years in the West. So enraptured with his first 10-day experience of the Falls during the King Expedition, he returned on his own in 1874 to make what would be his last published photographs of the West.