Grove Karl Gilbert (May 6, 1843 - May 1, 1918) was an American geologist who participated in early surveys of the American West. Born in New York, he attended the University of Rochester. He served as first geologist to George M. Wheeler's survey of the territory west of the 100th Meridian, and then joined John Wesley Powell's survey of the Green and Colorado River regions and the Rocky Mountains. These surveys were merged with the other two 'great surveys' of the American West to form the U.S. Geological Survey in 1879, whereupon Gilbert was appointed Senior Geologist. He spent the rest of his career and life with the USGS and was one of the most well-regarded geologists of his day, earning numerous awards and serving twice as President of the Geological Society of America.