A Democrat, he was most notable for his service as the 37th United States Secretary of the Treasury from 1885 to 1887 under President Grover Cleveland.

Manning also undertook self-study to compensate for his lack of formal education and became recognized for his expertise in topics as varied as finance and fine art.

As chair of the New York Democratic Party, Manning was a key supporter of Grover Cleveland's successful campaign for president in 1884.

As a trusted advisor, he provided input to Cleveland on political appointments and topics not directly related to his cabinet portfolio.

[2] He was educated in the local schools, and at age 11 he began working to help support his family, initially as a page for the New York State Assembly.

[4] Manning devoted significant time to self-study to make up for his lack of formal education, and developed expertise in political science, banking and finance, and fine art.

[3] As a trusted political advisor, Manning also provided input to Cleveland on appointees and issues that were not within Treasury's usual purview.

[3] After leaving the Treasury Department, Manning accepted appointment as president of the Western National Bank of New York.

[4][7] Manning's funeral took place at St. Paul's Episcopal Church in Albany, and was attended by President Cleveland and all but one member of the cabinet.

[12] These collectible notes are referred to as "Mannings" or "diamondbacks" due to their unusual reverse design, and because of their rarity they often sell for between $1,000 and $5,000.

[13] In 1898, engraver George T. Morgan created for the United States Mint a commemorative medal depicting Manning.

[15] During World War I, Manning was based at Gibraltar and escorted trade convoys to England and conducted anti-submarine patrols in the Mediterranean.