| Conventional Long Name: | Territory of Louisiana |
| Common Name: | Louisiana Territory |
| Nation: | United States |
| Subdivision: | Organized incorporated territory |
| Date Start: | July 4 |
| Year Start: | 1805 |
| Event End: | Renamed Territory of Missouri |
| Date End: | June 4 |
| Year End: | 1812 |
| P1: | District of Louisiana |
| Flag P1: | Star-Spangled Banner flag.svg |
| S1: | Missouri Territory |
| Flag S1: | Star-Spangled Banner flag.svg |
| Flag S2: | Flag of Louisiana.svg |
| Flag Type: | Flag of the United States |
| Flag: | Flag of the United States#Historical progression of designs |
| Image Map Caption: | Map of the Territory of Louisiana |
| Capital: | St. Louis |
| Government Type: | Organized incorporated territory |
| Title Leader: | Governor |
| Leader1: | James Wilkinson |
| Year Leader1: | 1805–1807 |
| Leader2: | Meriwether Lewis |
| Year Leader2: | 1807–1809 |
| Leader3: | Benjamin Howard |
| Year Leader3: | 1810–1812 |
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. The territory was formed out of the District of Louisiana, which consisted of the portion of the Louisiana Purchase north of the 33rd parallel (which is now the Arkansas–Louisiana state line).
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,"[1] which established the Territory of Orleans and the District of Louisiana as organized incorporated U.S. territories. With regard to the District of Louisiana, this organic act, which went into effect on October 1, 1804, detailed the authority of the governor and judges of the Indiana Territory to provide temporary civil jurisdiction over the expansive region.
On March 3, 1805, Congress passed legislation changing the District of Louisiana into the Louisiana Territory, effective July 4, 1805.[2]
The Louisiana Territory included all of the land acquired by the United States in the Louisiana Purchase north of the 33rd parallel. The eastern boundary of the purchase, the Mississippi River, functioned as the territory's eastern limit. Its northern and western boundaries, however, were indefinite, and remained so throughout its existence. The northern boundary with the British territory of Rupert's Land was established by the Treaty of 1818, and the western boundary with the Spanish viceroyalty of New Spain was defined by 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.
In the 1810 United States census, six counties in the Louisiana Territory, which included five counties in present-day Missouri and one county in present-day Arkansas, reported the following population counts:[3] [4]
| Rank | County | Population |
|---|---|---|
| 1 | St. Louis | 5,667 |
| 2 | Ste. Genevieve | 4,620 |
| 3 | Cape Girardeau | 3,888 |
| 4 | St. Charles | 3,505 |
| 5 | New Madrid | 2,103 |
| 6 | Arkansas | 1,062 |
| Louisiana Territory | 20,845 | |
The territorial capital was St. Louis.
On March 11, 1805, President Thomas Jefferson appointed Gen. James Wilkinson as the first governor of the Territory of Louisiana.[5] Wilkinson concurrently held the position of Senior Officer of the United States Army. Meriwether Lewis (1807–1809) served as the 2nd and William Clark (1813–1820) served as the 4th, and final, territorial governor.
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.[6]
The areas of the Louisiana Territory and Orleans Territory now cover several U.S. states, from the Gulf of Mexico to the border of Canada.
U.S. states once part of Louisiana territory include:
Canadian provinces once part of Louisiana territory include: