Daniel Florence Cohalan, American lawyer and politician of Irish descent, is born December 21, 1867, in Middletown, Orange County, New York, the eldest of five sons of Timothy E. Cohalan and Ellen Cohalan (née O’Leary), both Irish immigrants.

Cohalan graduates from Manhattan College in 1885, takes a master’s degree in 1894, and is given an honorary LL.D. in 1911. He is admitted to the bar in 1888, and practices law in New York City. In September 1889, he removes to the Bronx, practices law there, and enters politics, joining Tammany Hall, becoming an adviser to party boss Charles F. Murphy and later to John F. Curry. He is Grand Sachem of the Tammany Society from 1908 to 1911.

Cohalan is active in Democratic Party politics by 1900, drafting state party platforms and serving as a delegate to the national conventions in 1904 and 1908.

On May 18, 1911, Cohalan is appointed by Gov. John Alden Dix to the New York Supreme Court, to fill the vacancy caused by the election of James Aloysius O’Gorman as U.S. Senator from New York. In November 1911, he is elected to succeed himself. On December 28, 1923, he tenders his resignation, to become effective on January 12, 1924, claiming that the annual salary of $17,500 is not enough to provide for his large family.

Cohalan is a close associate of Irish revolutionary leader John Devoy and is influential in many Irish American societies including Clan na Gael. He helps to form the Sinn Féin League in 1907 and is a key organiser of the Irish Race Convention and the Friends of Irish Freedom (FOIF) on March 4-5, 1916. He is involved with the financing and planning of the Easter Rising in Dublin and is instrumental in sending Roger Casement to Germany in 1914. He is Chairman of the Irish Race Convention held in Philadelphia on February 22-23, 1919, and active in the Friends of Irish Freedom (1916–34).

When the United States enters World War I, Cohalan’s earlier work to obtain German assistance for Ireland becomes a liability, but he urges Irish Americans to support the war effort and to insist that self-determination for Ireland be included among the war aims. He opposes the peace treaty and the League of Nations and leads an Irish American delegation to the United States Senate Committee on Foreign Relations hearings, contributing to the defeat of the treaty in the Senate.

Cohalan strongly opposes President Woodrow Wilson‘s proposals for the League of Nations, on the basis that the Irish Republic had been denied a policy of self-determination at the Paris Peace Conference in 1919. In 1920, he works for the nomination of Hiram W. Johnson as the Republican Party candidate for president. His quarrels with Franklin D. Roosevelt begin in 1910, and he fights Roosevelt’s nomination for president in 1932 and 1936. He breaks with both Éamon de Valera and Irish American leader Joseph McGarrity in late 1919 on Irish American political direction.

In the aftermath of the Anglo–Irish Treaty, Cohalan and the FOIF back Arthur Griffith, Michael Collins and the Irish Free State. He visits Ireland in 1923 and supports William T. Cosgrave in the election of that year.

Cohalan dies at his home in Manhattan, New York, on November 12, 1946, and is buried on November 15 at the Calvary Cemetery in Woodside, Queens, New York. The Daniel F. Cohalan papers are in the possession of the American Irish Historical Society, New York.

State Senator John P. Cohalan (1873–1950) is one of Cohalan’s eleven siblings, and church historian Monsignor Florence Daniel Cohalan (1908–2001) is one of his nine children.