The Big Lost River in central Idaho is a premier trout fishing destination that flows approximately 135 miles through the stunning Lost River Valley. Starting in the Pioneer Mountains at elevations over 10,000 feet, this freestone stream gets its name from the way it eventually disappears into the Snake River Aquifer near Arco, Idaho. With the majestic Lost River Range and Pioneer Mountains providing a spectacular backdrop, the river offers diverse fishing experiences through its various sections, from mountain streams to tailwater fishing below Mackay Reservoir. The river supports a healthy population of wild and stocked trout, making it an attractive destination for anglers of all skill levels seeking both quantity and quality in their catches.