He was the oldest child of inventor Cyrus Hall McCormick Sr. (1809–1884) and philanthropist Nancy Fowler (1835–1923). He was born in Washington, D.C. on May 16, 1859. Cyrus Jr. married Harriet Bradley Hammond on March 5, 1889. They had three children: Cyrus Hall McCormick III was born September 22, 1890. Elizabeth McCormick was born July 12, 1892. Gordon McCormick was born June 21, 1894.