[2] His father and grandfather were both named John Moncure and active in the affairs of what was renamed Aquia Parish.

His mother Alice Peachy Gaskins (1774-1860) bore ten children, of whom Richard Cassius Lee was the seventh child and fourth son.

In 1849, he entered politics and won election to the legislature, which was then engaged in extensive revision of the state's legal code.

Although some questioned the validity of the wartime Constitution of 1864 (by delegates from Union-controlled areas, including Moncure's home Stafford County), Moncure also won election as one of three Court of Appeals judges elected under that constitution, and his fellows selected him as that Court's President in 1865.

[3] Before the American Civil War, Moncure was a relative moderate on the appellate court, vehemently dissenting from the decisions in 'Bailey v. Poindexter's Executor,' 55 Va. 132, 14 Gratton 132 (1858) and 'Williamson v. Coalter,' 14 Gratton 394 (1858),[4] both of which postdated the Dred Scott decision and declared testamentary manumissions void because a majority of Moncure's colleagues decided slaves were legally incapable of choosing freedom (although even preceding generations of Virginia judges, including John Marshall had used similar choice language in their wills).