[2] His brother, Franklin MacVeagh, was a Chicago wholesale grocer, banker and U.S. Secretary of the Treasury under President William Howard Taft.

He attended Yale University, where he was a brother of the Delta Kappa Epsilon fraternity (Phi chapter), and graduated tenth in his class in 1853.

[5] In 1903, he was a chief counsel of the United States before the Hague tribunal in the case regarding the claims of Germany, Britain and Italy against the republic of Venezuela.

[3] After the outbreak of World War I MacVeagh championed the cause of the Allies in an article "The Impossible Chasm", contributed to the North American Review in July 1915.

In his last article "Lusitania Day: May 7 1916", for the same magazine, he assailed the slowness of the American government in asserting its rights against Germany.