Mellette was the son of Charles Mellette and was born in Henry County, Indiana. He was educated at Marion Academy in Marion, Indiana. In 1862, Mellette entered Indiana University Bloomington as a sophomore and graduated in 1863. On October 6, 1864, he enlisted in Company H of the 9th Indiana Volunteers, serving as a conscripted soldier until mustering out on September 28, 1865. He served in the army as a substitute for his older invalid brother and experienced many humiliations as a result. In 1866, Mellette graduated from the School of Law at the Indiana University and went to Muncie, Indiana, where he began practicing law with Thomas J. Brady. On May 26, 1866, he married Margaret Wylie.
Career
Mellette was elected as district attorney for Delaware County, Indiana. In 1870, Mellette purchased the Muncie Times, a newspaper which became influential and prosperous under his tutelage. During that same year, Mellette was elected the county superintendent of schools. When his wife became ill, Mellette visited western states to find a climate that would be more beneficial to her. Mellette's family eventually settled in Springfield, Dakota Territory, for two years; and, Mellette served as register of the United States Land Office in Springfield until the land office was moved to Watertown, Dakota Territory, in 1880.
Political career in the Dakotas
In October 1885, the Republicans nominated Mellette for governor of Dakota Territory. In November 1885, Mellette ran unopposed for the office of governor; and, voters selected Huron as the temporary capitol of Dakota Territory. In 1889, voters approved the new constitution for South Dakota and elected Arthur C. Mellette as South Dakota's first Governor. On November 2, 1889, President Benjamin Harrison signed the proclamation to make South Dakota the fortieth state. Mellette County, South Dakota is named in his honor.
The family made what was meant to be a temporary move from Watertown to Pittsburg, Kansas in 1895. Mellette died May 25, 1896 while in Pittsburg. His body was sent back to Watertown and interred in Mount Hope Cemetery. , by sculptor John Lopez, was unveiled in 2012 and is placed in Pierre, South Dakota.Mellette’s former home in Watertown is maintained as a museum. In 2012, a statue of Mellette was unveiled in Pierre, South Dakota; it was the first statue placed on the city’s Trail of Governors.