I'm not exactly sure where "Indian Lands" is, but here are a couple of references that may help you.
The 1878 Illustrated Historical Atlas of Wisconsin wrote about "Indian Lands" in Marquette County. It said the lands upon the "south side of [Buffalo] lake were in market several years earlier than on the north, yet Jason Daniels and "Uncle" Jesse Dart settled in Montello in 1849, upon what was known as the 'Indian lands.' "
I suspect "Indian Lands" may include quite a large area in the 1850 census. In 1920, my great-aunt wrote that "much of Marquette County and some of the Green Lake County have long been known as 'Indian Lands' because they were the last places in Wisconsin which the Indians inhabited." In 1850 Green Lake County was still part of Marquette County.