They began their

numismatic careers as employees of John Haseltine. They started their own business in 1878. They were young and aggressive. Many dealers attempted to purchase the Bushnell collections from his heirs but the Chapmans were successful. Their catalog of the sale set a new high standard for descriptions of lots and helped establish the reputation of the Chapmans. They made use of photographic plates. In the beginning they were not allowed to present photographs of U.S. coins and paper money. Henry Chapman introduced legislation to allow such photographs.

Together they conducted 82 auction sales from 1879 to 1906. They had a disagreement after the H.P. Smith sale that caused them to conduct separate auctions after 1906.

In 2010, they were inducted into the CoinFacts Coin Dealer Hall of Fame.