A friend from northern Minnesota once told me he took his young son to the far upper reaches of the St. Croix River on a day trip. They stood in the water and his son asked "where does it go?"

A few days later I happened to visit the river at Afton State Park, and I took a photo and wrote a couple paragraphs titled "Where it Goes."

"Where the Yellowstone Goes," a new film out of Montana, seeks to answer the same question about an iconic Western river, the Yellowstone, which runs 690 miles from our oldest national park to the Missouri River. The filmmakers chronicled a 30-day float down the length of the river.

The film will show in Minneapolis for the first time on June 13 at Saint Anthony Main Theater, and 50 percent of ticket sales will be donated to American Rivers, a nonprofit group which works to keep the nation's rivers clean and wild.

The filmmakers describe their production this way:

Tickets are available for two screenings on June 13.

Trailer: