[3] Johnson quickly gained prominence among numismatists in the St. Louis area as a specialist in Roman-era coins and joined the American Numismatic Association at the age of eighteen.
[3] Johnson earned distinction for his seemingly encyclopedic knowledge and photographic memory despite his young age.
This partnership was short-lived, however, and by September of the next year Johnson bought Sutherland's share of the company and had sole ownership of the store.
By 1912, Johnson made annual trips to Europe to research, investigate, and collect ancient coins.
[6] Johnson fostered many relationships with people who went on to become prominent numismatists, and was well known for his openness and enthusiasm in spreading numismatic interests in others.
During the Great Depression, Johnson took in a young girl named Mary Cruzan who had been abandoned by her parents.