Walling, Henry Francis & Gray, Ormando Willis
Henry Francis Walling (1825-1888) was an American civil engineer and cartographer. He published or co-published atlases of several states of the northern United States, including Massachusetts, Maryland, Michigan, Pennsylvania. Ohio & Illinois, which included county maps and town plans, collaborating on a number of these with Ormando Willis Gray. He joined the newly-formed United States Geological Survey in 1883, and in 1884 was assigned to duty for the geodetic survey of Massachusetts in preparation of the state maps.
Walling, Henry Francis & Gray, Ormando Willis
Ormando Willis Gray (1829-1912) was an American civil and topographical engineer and cartographer. He collaborated with Henry Francis Walling in several US state atlases, of which his output included atlases of Massachusetts, Pennsylvania, Maryland, Ohio. He also published "Gray's atlas of the United States" under his own name.