The structure had been erected by Mr.Jerome for the use of the Jockey Club, but was leased to the Union League for a term of ten years.

Among the early honorary members of the Union League were Abraham Lincoln, General U.S.Grant, General W.T.

Sherman, Lieutenant-General "Phil" Sheridan, Major-Generals Burnside, Wright, and Hancock, Admiral David G.Porter, and Rear-Admiral Bailey.

The active membership of 1870 included such names as William Cullen Bryant, William M.Evarts, Whitelaw Reid, Parke Godwin, Horace Greeley, Chester A.
Arthur, Thomas Nast, Joseph H.Choate, Eastman Johnson, George P.
Putnam, Daniel P.Appleton, Dr.Samuel Osgood, George Griswold, E.D.
Stanton.
To the name of the Union League is inevitably linked that of the Manhattan Club, for, the Civil War once at an end, the latter became the expression of the political aims and aspirations of the Democratic Party as the former was of the Republican.

The Manhattan had its origin in the turmoil of the election of 1864, and the defeat of the Democratic candidate, General McClellan.