If the Sigrid Jesperson in the info I posted is the same Sigrid Jesperson in the photo, it can't be a high school sorority because Sigrid would be 23 in that photo. This also leads me to wonder about when HS sororities first started.

Benzgirl mentioned something about Scandinavians settling in the Midwest, and that's what I thought too. My 6th grade teacher was Sister Agnes Iten, CSJ -- and she was very proud of her Minnesota roots!