By virtue of his descent from Captain Perry, Belmont became a member of the Rhode Island Society of the Sons of the Revolution.

[3] During his first term, he was a member of the committee on foreign affairs; noted for his cross-examination of James G. Blaine, the former secretary of state.

The cross-examination concerned Blaine's relations with a syndicate of American capitalists interested in the development of certain guano deposits in Peru.

An attempt was made to show that Blaine's efforts toward mediation between Chile and Peru were from interested motives.

When the Consolidated National Bank of New York was organized on July 1, 1902, the fourteen directors included individuals such as Belmont, John W. Griggs, Henry C. Brewster, George Crocker, and Mortimer H.

[6] In 1906, Belmont became "permanent president" of the National Publicity Bill Organization, which fought for campaign finance disclosure.