The Wisconsin Historical Society maintains an online dictionary of Wisconsin history. According to that resource, the word “wanagan” had several different uses in the context of Wisconsinite historical logging:

“1. Where the camp stores are kept. 2. The payroll charges for such goods. 3. In Wisconsin it was also the cook’s raft which went down the river behind the logs. It was tied to a tree on shore overnight. 4. Wherever camp was made on a river-drive and the men paid Same as ark, shanty-boat.”

None of those are close to the meaning I was searching for. Here’s another slightly different version again.