Marshall was born in Maryland in Prince George County per the census of 1850. He was born in 1844. His parents were John Henry Sothoron and Elizabeth Magruder Somervell. Marshall was living with his family including many siblings in St. Mary' s County, Maryland in 1850. His father was a Planter. He was a student in school in 1860 and the family lived in St. Mary's County near Charlotte Hall Post Office.
War came to Maryland and the South in April of 1861. He enlisted as a Private in Company I of the 1st Maryland Infantry Regiment at Richmond on August 4th. He was absent sick in hospital on muster roll for period of Sept to Oct. He was still sick in hospital from Oct 1st on muster roll Nov to Dec. He was on a list sent sick from the regiment sent to Manassas with Remittent Fever since 1 Oct. Marshall's brother, Webster Sothoron also enlisted as a Private in the same regiment.
Marshall was later in January 1864 appointed Assistant Paymaster, CSN on the C.S.S. Chattahoochee. He served on the ship until June. In the Spring of that year while the ship was in for repairs at Columbus, Georgia Lt. George W. Gift the commanding officer led a mission to Apalachicola in an attempt to board and capture one of the blockading vessels there. Marshall was among the men from the C.S.S. Chattahoochee in that mission. After that mission failed and the party returned to the ship Marshall was then appointed Assistant Paymaster Provisional Navy on 2 June 1864. and then was transferred to the C.S.S. Sampson and Savannah Station. The ship was a gunboat on combat duty, patrolling the Savannah River with the defense force of Flag Officer W. W. Hunter, CSN. In early December 1864 she joined with Macon and Resolute in an expedition to destroy the Charleston and Savannah Railway bridge spanning the Savannah River, and sustained considerable damage. Prior to the capture of Savannah by General Sherman on 21 December 1864 Sampson was taken up the river to Augusta, remaining there until the end of the war. Assistant Paymaster Sothoron was mentioned by Flag Officer Hunter as still in service in Jan of 1865. He was paroled at Augusta, Georgia on 9 May 1865.

After the war Marshall returned to Maryland. He was living with his family on his father's farm and working as a laborer along with many of his siblings in 1880. He never married and continued to live in Maryland with his brothers and sisters. His mother passed away in 1888 and his father died in 1893 while at a hotel in Washington, D.C.
Marshall died in 1923.