Ladenburg Thalmann became one of the most influential private merchant banking firms, a major financial intermediary between America, Great Britain, and the European Continent.

It played an important role in financing the growth of American industry—particularly America’s railroads, utilities, and emerging industries—through the early twentieth century and was among the few investment banks to prosper during the Great Depression.

In the early part of the 20th century, many notable businessmen joined Ladenburg Thalmann as partners, including Gerson von Bleichröder[dubious – discuss] and Benjamin Seymour Guinness and Walter Tower Rosen.

Another source was the black markets in Tangiers, Beirut, Istanbul, and elsewhere, from the sale of commodities such as gold, platinum, diamonds, precious stones, and Swiss watches.

Virtually every European currency was acquired, as well as South American and Far Eastern currencies; a statement from mid-1944 prepared for Winston Churchill cited the cumulative acquisitions to that date as being 600m French francs, 20m Belgian francs, 8m Dutch guilders, 3.5m Norwegian kroner, 3.5m Danish kroner, 6m Reichsmarks, 8m Spanish pesetas, 16m U.S. dollars, and 0.5m Argentine pesos.

Tobacco was deemed a more useful bribe to badly-paid Spanish border and customs officials, and hundreds of tons were shipped in from Latin America, and North Africa post-TORCH, blended and packaged in Gibraltar, and handed to Musson's operation to maintain the smuggling cover.

Securities America Inc. was acquired by Ladenburg Thalmann from Ameriprise Financial in November 2011 for $150 million in cash and potential future payments.