American forester and field assistant in tropical forestry for Yale University, later associated with New York Botanical Garden. From Los Angeles, Cooper was employed by the United Fruit Company in the 1920s. He was tasked with exploring the virgin forests and marginal fields of the banana plantations of Bocas del Toro, Panama, an area then virtually unexplored since J.H. Hart's visit in 1875. With George Slater, Cooper brought a collection of about 133 numbers of trees and shrubs to the Yale School of Forestry from these explorations in 1926-1927, a high percentage of which turned out to be new species. In 1927-1928, working alone on behalf of the United Fruit Company, Yale, the Field Museum of Chicago and New York Botanical Garden, Cooper collected 330 numbers in Bocas del Toro, again yielding many novelties. He also collected plants in Liberia (for Yale) and co-authored a report on the country's evergreen forests with Samuel Record (1931). In 1933 he travelled to the Caribbean for New York Botanical Garden.

Sources:
Anon., 1929, Field Museum of Natural History Reports, 7(3): 394
B.M. Boom, 1996, "Botanical expeditions of the New York Botanical Garden", Brittonia, 48(3): 310
E.D. Merrill, 1932, "Garden cooperates with G. Proctor Cooper, 3rd" Journal of the New York Botanical Garden, 33(395): 237-238
G. Proctor Cooper and S. J. Record, 1931, The evergreen forests of Liberia: a report on investigations made in the West African republic of Liberia by the Yale University School of Forestry in cooperation with the Firestone Plantations Company
P.C. Standley, 1929, "Studies of American Plants I", Field Museum of Natural History Botanical Series, 4(8): 197.