The Territory of Louisiana or Louisiana Territory was an organized incorporated territory of the United States that existed from July 4, 1805, until June 4, 1812, when it was renamed the Missouri Territory.
Louisiana Territory was formed out of the Indiana Territory-administered District of Louisiana, which consisted of all Louisiana Purchase lands north of the 33rd parallel. The 33rd parallel now forms the southern border of Arkansas and the northern border of Louisiana. The territory's predecessor, the District of Louisiana, as well as the District of Orleans, were formed from the lands acquired by the United States in the Louisiana Purchase, in which colonial Louisiana was purchased from France.
The Eighth Congress of the United States on March 26, 1804, passed legislation entitled "An act erecting Louisiana into two territories, and providing for the temporary government thereof," which established the Territory of Orleans and the civil District of Louisiana.
This act, which went into effect on October 1, 1804, expanded the authority of the governor and judges of the Indiana Territory to provide temporary jurisdiction over the District of Louisiana.
On March 3, 1805, Congress enacted legislation organizing the District of Louisiana into the Louisiana Territory, effective July 4, 1805.
The Territory was governed similarly to Indiana Territory.
The Louisiana Territory included everything in the Louisiana Purchase north of the 33rd parallel (the southern boundary of the present state of Arkansas).
The southern and western boundaries with Spanish Texas and New Mexico were not fully defined until the Adams–Onís Treaty of 1819.
The Louisiana Territory had five subdivisions: St. Louis District, St. Charles District, Ste. Genevieve District, Cape Girardeau District, and New Madrid District.
In 1806, the territorial legislature created the District of Arkansas from lands ceded by the Osage Nation. The remainder was known as the Upper Louisiana Territory.
The seat of government was in the town of St. Louis.
The first territorial governor was James Wilkinson, appointed by President Jefferson and concurrently holding the position of Senior Officer of the United States Army.
Meriwether Lewis (1807–1809) and William Clark (1813–1820) served as the second and third Louisiana Territory governors, respectively.
On June 4, 1812, the Twelfth U.S. Congress enacted legislation which renamed Louisiana Territory as Missouri Territory, in order to avoid confusion with the recently admitted State of Louisiana.