The portion of Idaho the 46 degrees north latitude marked a dividing line in Idaho in 1860. Everything north of that point was part of Washington Territory. To be specific, it was part of Spokane County.
According to the federal census taken in 1860, there was no white population in that area. Some people who were living in what is now the Bear Lake area were included in the Cache County, Utah Territory federal census of 1860.
A census of Idaho Territory was taken in 1870. All of those records have survived and have been indexed. However, it is important for researchers to note that the Nez Perce County census included the unorganized region of Kootenai.
Also, the Cache County, Utah census for that year included part of Franklin County, as well as part of Bear Lake.
When the 1880 census was taken in Wyoming, it included the areas of Yellowstone National Park that is located in Idaho. The Idaho Genealogical Society has created an index of the 1910 federal census.