How do I find out if my ggg-grandma was an indian?

I could really use some direction. I am new to GenWise, and somewhat new to researching my ancestors.

I am told through family stories that my g-g-g-grandma must have been indian. When I was a little girl, my gr-uncle came to live use and idenitifed some photos for us. I have a photo of her and of her parents. Her parents do not look indian, they are white. Maybe it was the way they took photos back then, I dont know. But she had really long sold black hair and darker skin than her parents. Again, it could've been the photo.

I do know she was born in 1877 in Monroe Co., WI. If she was indian, and was "adopted" or care for by a white couple, would their be a record of this somewhere? If so where do I begin to search?

I do know that her obituary doesn't mention about being indian. The census doesn't notate indian status either. Any help would be appreciated.