 He moved to New Orleans during the invasion of Louisiana by British forces, joined the Orleans Volunteers, and participated in the battles of December 23, 1814, and January 8, 1815, the latter commonly called the battle of New Orleans.After relocating to Donaldsonville, the seat of Ascension Parish south of Baton Rouge, Nicholls was appointed a Louisiana district judge in 1836.In 1840, he wrote a memoir of his family's journey from Maryland to the Atakapas country in south Louisiana.