On April 10, 1805, the Territorial Legislature organized 12 counties (starting from the southeast corner moving west and north): Orleans, Lafourche, German Coast, Acadia, Iberville, Attakapas, Pointe Coupée, Opelousas, Rapides, Concordia, Natchitoches, and Ouachita.

The western boundary with Spanish Texas was not fully defined until the Adams–Onís Treaty was negotiated in 1819.

The Orleans Territory was the site of the largest slave revolt in American history, the 1811 German Coast Uprising.

Judges of the Superior Court were John Bartow Prevost (1804–1808), Ephraim Kirby (1804) (died en route to New Orleans), Peter Stephen Du Ponceau (1804) (declined President Thomas Jefferson's appointment), William Sprigg (1805–1807), George Mathews, Jr. (1805–1813), Joshua Lewis (1807–1813), and Francois Xavier Martin (1810–1813).

At its first meeting on December 3, 1804, the territory's Legislative Council consisted of Julien de Lallande Poydras, William Kenner, John Watkins, William Wikoff, Benjamin Morgan, Eugene Dorcier, and George Pollock.