Myron H. Southwick was born around 1842 in Michigan to Rawson Southwick and Emily B. Hutchins. His father was a farmer who owned $3,000 of real estate and $425 of personal property in 1860. Southwick attended school in Deerfield, Michigan, before beginning work as a farmer. He enlisted in the Union army on February 16, 1864, and mustered in as a private in Company H of the 8th Michigan Infantry on February 29, 1864. He became a hospital steward on June 1, 1865, and he mustered out in Washington, D.C., on July 30, 1865.
Southwick returned to Michigan after the war, and he married Louisa Havens on November 29, 1867. They had at least two children: Myrtle, born around 1872; and Lura, born around 1874. The family moved to Union, Iowa, in the late 1860s, and by 1870, Southwick owned $2,600 of real estate and $1,000 of personal property. In 1880, he was working as a county auditor in Adams County, Iowa. He applied for a federal pension in June 1880, complaining of rheumatism. The family moved to Gage County, Nebraska, in the early 1880s, and Louisa died there around 1887. He married Cordelia M. Henika in Greeley, Colorado, on September 20, 1888, but they apparently divorced by 1900. By 1900, Southwick was working as an insurance agent. He moved to Los Angeles, California, in the early 1900s, and in 1918, he was admitted to the local National Home for Disabled Volunteer Soldiers. By then, he was suffering from myocarditis as well as chronic acute rheumatism. He married Lucretia Mott Phillips in El Centro, California, on February 10, 1922, and spent the next several years in San Diego. He died there on July 7, 1929.