He and his brothers received a private education, although their father died in 1849 when Eustace was a boy.

Eustace was promoted to captain in 1863 and retired as a result of his severe abdominal wound at the Battle of Gettysburg.

[4] Voters from Pulaski and Giles Counties elected this Gibson to represent them at the Virginia Constitutional Convention of 1868, and voters from his native Culpeper County elected his brother J.C. Gibson as one of their representatives.

He defeated local Judge Robert S. Brown, who ran in part on a temperance platform.

While a member of the Forty-ninth Congress, he served as a chairman of the Committee on Expenditures in the Department of Justice.