Congress attached the country west of the Mississippi river and north of the State of Missouri to the Territory of Michigan for temporary judicial purposes.

The evidence

• “The interior was yet sparsely settled. By the act of June 28, 1834, congress having attached to the Territory of Michigan, for judicial purposes, all the country "west of the Mississippi river, and north of the State of Missouri," comprising the whole of what is now the State of Iowa, all of the present State of Minnesota west of the Mississippi river, and more than half of what is now the Territory of Dakota, the legislative council of Michigan Territory extended her laws over the whole area, dividing it on the 6th of September, 1834,. by a line drawn due west from the lower end of Rock island to the Missouri river into two counties : the country south of that line constituting the county of Des Moines; north of the line, to be known as the county of Dubuque. This whole region west of the Mississippi was known as the Iowa district.”

  1879-history-of-rock-county/01-wisconsin-antiquities-indians-territory.md, PDF p. 36

  Butterfield, C. W., et al. The History of Rock County, Wisconsin: its early settlement, growth, development, resources, etc. Chicago: Western Historical Company, 1879. Cornell University Library via the Internet Archive, archive.org/details/cu31924028871585.

  Grade A: Found on a page of one of our sources