Marcus Junius Parrott was born on October 29, 1828 in Hamburg, South Carolina. He graduated from Dickinson College, Carlisle, Pennsylvania in 1849 and afterward studied law at Cambridge Law School in Massachusetts. He was admitted to the bar and in 1851 established a law practice in Dayton, Ohio. In October 1853, he was elected to a two-year term in the Ohio house of representatives, resigning at the close of the first year.

Parrott moved to Kansas Territory in 1855, first living at the Methodist Mission near Westport, Missouri before settling in Leavenworth. From 1855 until admission of Kansas to the Union in 1861, he was politically active in the Kansas Territory's free-state movement and a personal witness to the armed conflict between pro-slavery and free-state factions. He served as court reporter of the first session of the Territorial supreme court in 1855 and as legal defense for many free-state prisoners, including Governor Charles Robinson. Parrott was named to the Free-State party's Territorial Executive Committee at its 1855 Topeka Convention, and in 1857 was elected the Territory's first free-state Delegate in Congress, representing the Territory at the Thirty-fifth and Thirty-sixth Congresses, which immediately preceded Kansas statehood.

Parrott was defeated as a Congressional representative in later Kansas elections, including its first senatorial election, but remained active in Kansas politics through 1876. He died in Dayton, Ohio on October 4, 1879.

For additional biographical information on Parrott, see H. M. Moore, Early History of Leavenworth City and County, University of Kansas Libraries, available at call number RH C9675.