Short answers, pulled from the story.
The Louisiana Territory officially came into existence on the 4th of July 1805 when the name change from District of Louisiana became effective. This new territory was established by an act passed by Congress on the 3rd of March 1805.
President Thomas Jefferson appointed General James Wilkinson as the first governor of the Louisiana Territory on the 11th of March 1805. He simultaneously held the position of Senior Officer of the United States Army while serving in this role.
On the 4th of June 1812 the Twelfth U.S. Congress enacted legislation renaming Louisiana Territory to Missouri Territory. No further legal documents used the term Louisiana Territory after this date for this specific region.
The land once covered by the Louisiana Territory now forms parts of multiple current U.S. states including Arkansas Missouri Iowa Nebraska Kansas Oklahoma North Dakota South Dakota Minnesota Wisconsin Illinois Montana Idaho Wyoming Colorado Utah New Mexico Texas and Canada. Portions of present-day Canadian provinces also contain lands that were part of the historical territory.
Five districts formed the initial administrative structure of the territory including St Louis District Ste Genevieve District Cape Girardeau District New Madrid District and St Charles District. In 1806 the territorial legislature created the District of Arkansas from land ceded by the Osage Nation.