Horace Jay Mellum was born to Norwegian parents, Ole Halvar Mellum and Anna Louisa Aspaas Mellum. He attended Chicago public schools, Chicago Business College, Morgan Park Military Academy, and Northwestern Military Academy, Highland Park, Illinois. In 1895, Mellum enlisted in Company M, First Infantry, Illinois National Guard, where he served until 1908. This service sent him to Cuba in 1898 in the Santiago campaign.
Employed as a stenographer for the Griffin Wheel Company, Chicago, Mellum attended evening classes at the John Marshall Law School and received his LL.B. degree in 1910. He engaged in a general law practice until 1916 when he was hired as secretary of the Thomas B. Jeffery Company, a Kenosha, Wisconsin, auto manufacturer which evolved into Nash Motors and the Nash-Kelvinator Corporation. He remained with the company until his retirement at age 75 in January 1952.
During his years in Kenosha, Mellum was active in professional, military, and civic organizations. Affiliated with the Kenosha Boy Scouts, the Chamber of Commerce, and various Masonic orders, he resumed his military interest by helping organize and becoming the head of the Kenosha Provisional Battalion, 1917-1920, a unit formed to replace National Guard troops serving in World War I which performed guard and ceremonial duties and provided pre-enlistment training to soldiers. He remained in the National Guard until 1941 when he retired with the rank of colonel.
Mellum developed expertise in worker safety and vocational rehabilitation and from 1926 to 1931 was president of the Wisconsin Association for the Disabled, an organization devoted to aiding crippled children and disabled adults. From 1920 to 1951, he served on the state advisory committees on workmen's compensation and unemployment compensation and on his retirement was made an honorary life member of the latter by the Industrial Commission of Wisconsin. A member of the Automobile Manufacturers Association, he also served as vice president of the Wisconsin Manufacturers Association for several years. Mellum was a talented public speaker and presented many speeches on patriotic and automotive topics to Kenosha organizations and trade groups.
Married to Nellie Eleanor Miller, of Winterhur, Switzerland, on June 24, 1903, Mellum had one son, Horace J., Jr. After retirement, he returned to Chicago and became active in the Chicago Bar Association.
