Nestled in the heart of the Ozarks, right on the Arkansas-Missouri border, lies Mammoth Spring, one of the largest natural springs in the United States. The constant flow of cool, clear water from the spring feeds into Spring River, where just downstream, the Mammoth Spring Dam holds back the headwaters, creating an angler’s paradise for trout fishing.

A Spring-Fed River with Cold Water Year-Round

Mammoth Spring pours out over 9 million gallons of water every hour at a consistent temperature of 58 degrees. This makes it the perfect habitat for rainbow trout, which thrive in cold, oxygen-rich water. The dam itself forms Spring Lake, which spills over and creates the upper section of Spring River — a productive and scenic fishery that's popular year-round.

Thanks to the spring-fed nature of the river, trout don’t just survive here — they flourish.

Trout Fishing Opportunities Below the Dam

The stretch of river directly below the dam is managed as a catch-and-release area for part of the year and supports a healthy population of stocked and holdover rainbow trout. The Arkansas Game and Fish Commission stocks thousands of trout annually, and many of them grow to impressive sizes thanks to the nutrient-rich flow and consistent temperatures.

Anglers can fish from the banks, wade the shallow sections, or even float downstream in kayaks or rafts. With riffles, deep pools, and rocky runs, it’s a river that keeps things interesting for fly fishers and spin anglers alike.

Popular techniques include:

• Fly fishing with nymphs and streamers
• Spinners like Rooster Tails or Panther Martins
• Drifting live bait or PowerBait through the current

The crystal-clear water allows for sight-fishing in many areas, especially early in the morning or late in the day when the light is low.

Mammoth Spring State Park: A Place to Slow Down

Mammoth Spring Dam is inside Mammoth Spring State Park, a beautifully maintained area that offers fishing, hiking, picnicking, and wildlife viewing. Near the dam, there’s a historic hydroelectric plant dating back to the early 20th century, as well as an old Frisco train depot that’s been converted into a museum, giving visitors a glimpse into the town’s rich history.

If you’re traveling with family or just looking to relax between casts, the park has plenty of open space, trails, and educational exhibits to explore.

Best Times to Go

Trout fishing below Mammoth Spring Dam is productive year-round, but the cooler months often bring the best action and fewer crowds. Early spring and late fall are especially good times, with fish more actively feeding and willing to chase a well-placed lure or fly.

If you're looking to catch trout during Arkansas’s mild winter, this is one of the best cold-water fisheries.

Whether you're a seasoned fly angler or just getting into trout fishing, Mammoth Spring Dam offers a unique experience. With its combination of natural beauty, cold clear water, and well-managed trout populations, it's a destination that feels both remote and accessible. So grab your rod, pack a lunch, and spend a day exploring one of Arkansas’s most underrated trout waters.