Michigan Territory was a territory of the United States in the early 19th century , between June 30 , 1805 and January 26 , 1837 , when it became Michigan , the 26th state of the Union . The Territory of Michigan was an organized incorporated territory of the United States that existed from June 30 , 1805 , until January 26 , 1837 , when the final extent of the territory was admitted to the Union as the State of Michigan .