Sarah McClanahan White, Marcellus' mother, died in 1856. I have not found the White family on the 1860 census. I have found one potential match that shows Marcellus, his wife and his father in Ray County, Missouri.
here. Sometime around 1860 Marcellus married Mary J. Tosh. I have researched all of the marriage records in Roanoke County, Virginia, but have found no record of their marriage.
Marcellus fought in the Civil War and served with the Salem Flying Artillery, made up of soldiers from Roanoke County, Virginia. He was captured soon after the battle of Gettysburg and spent many months as a POW. He was mustered out of service at Appomattox Court House, where his unit was noted as having fired the last round of the Civil War.
Following the war the White family are found in Ray County, Missouri. Marcellus and Mary had 6 children.
1. Try to locate a birth record for Thomas E. White. It may indicate where the White family was in 1860.
2. Search Virginia newspapers to see if there is information about any business owned by the Whites in the 1850s.
3. Continue to search for definitive documentation that Marcellus is indeed from Roanoke County, Virginia.
Other posts about Marcellus:
A timeline - Marcellus White
Marcellus White, Civil War Prisoner of War
Who is "My" Marcellus?
The search for Marcellus' land
The Civil War remembered - May 14, 1861