Mark Finnicum was born on December 25, 1823 in Ohio, and was a merchant in Fennimore, Wisconsin at the start of the war.

On July 20, 1861 he became captain of Company H, 7th Wisconsin Infantry. He was elected to major in early 1863. At Gettyburg he took over command of the 7th when its colonel, William W. Robinson, took over command of the Iron Brigade.

Finnicum was promoted to lieutenant colonel in January of 1864. He was wounded at Spotsylvania but returned to duty on May 31. He resigned his commission on December 17, 1864.

He died November 4, 1912 in Pulaski County, Kentucky.