McCormick was born July 26, 1849, on the family plantation known as Walnut Grove in Rockbridge County, Virginia.

[3]: 39 Politically active and a major donor to the Republican Party, in 1889 McCormick was appointed as Second Secretary of the American Legation in London, where he served from 1889 to 1892, under Minister Robert Todd Lincoln, eldest son of the late President Abraham Lincoln.

McCormick presented his credentials on April 29, 1901, and served through McKinley's assassination at the Pan-American Exposition on September 14, 1901.

[5] On September 26, 1902, Roosevelt appointed him to St. Petersburg to serve as United States Ambassador to Imperial Russia.

See Chaim M. Rosenberg, The International Harvester Company: A History of the Founding Families and Their Machines (McFarland, 2019).