After his graduation in 1907, Lewisohn started working for the New York law firm Simpson Thacher & Bartlett.
In 1910 he joined his father's law firm Adolph Lewisohn & Sons, where he kept serving as lawyer.
In the President's Conference on unemployment of 1921 [4] he served in as member of Economic Advisory Commission.
[5][6] Lewisohn became a member of the New York Stock Exchange in 1927; Director of the Equitable Life Assurance Society of the United States, where he served as director until his death; member of the New York State Commission of Correction in 1928, and many other functions in the industry, government, and cultural industry.
"[1] Their third daughter was Elizabeth Eisenstein, a notable historian of the French Revolution and early 19th-century France.