James Thomas was born in 1785 in St. Mary's County, Maryland, and pursued an education that included time at St. John's College and a degree from Charlotte Hall Military Academy. He later earned a doctor's degree in medicine from Philadelphia. Thomas held various public service roles, including justice of the peace and member of the Levy Court of St. Mary's County, and served in the Maryland State Senate. He was elected governor of Maryland in 1833, during which he played a key role in resolving disputes between the Chesapeake and Ohio Canal Company and the Baltimore and Ohio Railroad. After his term ended in 1836, he retired to "Deep Falls," St. Mary's County.

James Thomas's political career reveals an ideological agility that balances regional economic interests with public safety. His support for infrastructure projects like the Baltimore and Ohio Railroad demonstrates a strategic focus on economic development. However, his establishment of a state militia following the 1835 Baltimore riots indicates a readiness to enforce order, showcasing a calculated approach to maintaining stability. This juxtaposition of economic pragmatism with a firm stance on public safety highlights a nuanced political identity.