Gergen Reservoir   Be the first to submit input for Gergen Reservoir. If you have info on Gergen Reservoir, Carter County, Montana please submit it here to improve this web site.          These outdoors activities are available near Gergen Reservoir.   Public Lands Near Gergen Reservoir: Medicine Rocks State Park, Montana, 27 miles away Devils Tower National Monument, Devils Tower - WY, 61 miles away   Camp Grounds Near Gergen Reservoir: Lantis Spring Campground, Carter County, 5 miles away   Ski Areas Near Gergen Reservoir: Terry Peak, South Dakota, 67 miles away       1100 foot drop, 6 lifts, 24 runs