Why is the top half of Michigan considered Michigan and not Wisconsin?

It came about as a result of the Toledo "War".

The Toledo War, 1835-1836, was a boundary dispute between Michigan and Ohio. Michigan argued, rightly so, that a strip of land on the border with Ohio, which included the City of Toledo, belong to them. Michigan wasn't a state yet, and Ohio was, so pressure was brought to bear on Michigan by the federal government to give up about half of the small strip of land in exchange for the Upper Peninsula. Which they did.

Michigan, is essense, won the war. Because of the large amount of land (and water) in the Upper Peninsula, Michigan is the 10th largest state in the United States and 1st largest east of the Mississippi River.

And, it's a good thing for the Yoopers that the Upper Peninsula ended up in the superior state of Michigan and not Wisconsin.

Well, I beg to differ: they are connected. There's Mackinac Island in the middle of the straits between the two, the narrows between Lake Michigan and Lake Huron. But as to why the Upper Peninsula (UP, we called it, when I was in school at U. of M.) is not part of Wisconsin, it is strange, but I never heard. Not really. Piecing together what I have heard, though, and what I found in Wikipedia, it seems the main interests in the UP for many years were lumber (it's almost entirely wooded) and mining. The territories that are now Michigan were ceded by various Indian tribes, and by the French and the English as the whole North American continent was being explored and fought over and etc. I suppose the interests that held the lumber and mining in the UP had closer ties to the lower portion of Michigan than they did to Wisconsin.

But isn't it odd that searching on "Michigan history" in Wikipedia did not touch on this particular issue.

The UP is part of Michigan because it is to good for Wisconsin

Not enough cheese?