Watch Montana Amazon for Free: How to Stream the Movie Online at 123Movies. . The Dunderheads are an eccentric Montana family who've been in the mountains for far too long. Now one step ahead of the law, matriarch Grandma Ira flees to Canada with her two wildly dysfunctional teenage grand kids, across the American West into a comic collision with the mainstream world. Montana Amazon is a both funny and poignant fable on the nature of the human family.