The Flathead Beacon has an article that begins… Every January, during the first half of the 20th century, all eyes in the Flathead Valley would turn to the lakes and ponds. As the days got colder, a thin layer of ice would form on top of the water, growing thicker by the day. Once it was at least six inches thick, one of the most important harvests of the year would begin. Read the full article here. There are some nice additional photos in the article as well.