[2][3] Horowitz joined Salomon Brothers in 1955 after graduating from law school and was made general partner in 1967.
He would then serve on the executive committee of Salomon Brothers until its sale to Travelers Group in 1997.
[4] After the merger between the Travelers Group and Citicorp in 1998, he served as a managing director of Citigroup's Institutional Clients Group until his retirement in 2019, having served the firm and its predecessor for 60 years.
[5] In addition to his banking career, he served as a key delegate of industry trade groups and founded the Public Securities Association, a trade association of banks, dealers and brokers that underwrite, trade and sell U.S. federal, state and local government securities, in 1967 that later became the Bond Market Association and served as its chairman in 1979.
[6][7] He also chaired the Securities Industry Association in 1991, having served as its director from 1984 to 1986 and 1988 to 1990, as well as its treasurer in 1987.