He worked in various executive positions at Carnegie Steel Company, rising to President, and later served as an ambassador for the United States to Switzerland, the Ottoman Empire, Italy, and Germany.

Mud clerks were the steel industry's representatives on the river wharf, responsible for tracking the shipping of goods: the arrival of raw materials and the departure of finished products.

To ensure efficiency and success, mud clerks lived 24 hours a day in small sheds on the riverbank.

[2][4] Leishman’s social and business connections provided entrée into an extraordinarily exclusive circle of sixty-odd families, called the South Fork Fishing and Hunting Club.

It was conceived as an idyllic summer colony, bought and developed by Henry Clay Frick in Cambria County, Pennsylvania, a short, convenient train ride away from the smoke and soot of Pittsburgh's industry.

Armed with a pistol and a sharpened rat-tailed file, Berkman gained easy access to the headquarters of Carnegie Steel and found his way into the second floor private office of the chairman, 43-year-old Henry Clay Frick.

This was thwarted when Frick engaged a stratagem to orchestrate the ouster of the man who had saved his life from the presidency of Carnegie Steel, and his removal from the Western Pennsylvanian business scene.

Under pressure from both men, Leishman withdrew from Carnegie service in June 1897, to accept the appointment by President William McKinley as United States Ambassador to Switzerland.

[8] Years later, as a board member of the Equitable Life Insurance Company, Frick used a similar scheme to arrange the removal of James Hazen Hyde (the founder's only son and heir) from the United States to France by seeking an appointment for him to become United States Ambassador to France.

While serving abroad, the Leishmans were often in Paris, at Deauville, Monte Carlo, or in the Swiss or Italian lakes, always a part of a glittering circle of celebrated American and European friends.

[21] As a result of the impasse between himself and Kaiser Wilhelm II which was created by his daughter Nancy's marriage to Karl von Croy, Leishman left Berlin and retired to private life in 1914.