Wm. Clark & Son (1839 - 1843)
Clark & Son (1837: 1845-46)
Wm. Clark (1844: 1847-60)
"Of William Clark's life only the span from 1837 to 1860 is known. Clark & Son, Wm. Clark & Son, and Wm. Clark as math. inst. makers are listed in the Philadelphia directories as listed above. In 1839 Clark, John, is listed at 122 S. Front same address as William Clark is listed in 1844. It may be possible that this is the John Clark of Washington who is listed there from 1858 to 1890 as a mathematical instrument maker."
"In the Philadelphia Circulating Directory for 1838, arranged by J. R. Savage, page 102 is the following: WILLIAM CLARK & SON Engineers and Surveyors Instruments Manufactory, No. 122 South Front Street Above Dock, Philadelphia."
Reference: Smart, Charles E. The Makers Of Surveying Instruments In America Since 1700 Troy, New York: Regal Art Press. 1962