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Marshall Mining District
 The Marshall Mining District is located on the lower Yukon River, where 130,000 ounces of placer gold was produced from the Willow Creek, Kako and Stuyahok placers. Plutonic-hosted lode gold prospects also occur in these areas. Radiometric ages for the plutonic rocks are from 61 to 71 million years, the same as those for Donlin Creek and most other plutons in the Kuskokwim Mineral Belt.
Gold occurs in quartz veins and breccia associated with altered andesite and diorite on upper Willow Creek at the Arnold Prospect. 85,000 ounces of placer gold was produced from Willow Creek before World War II suspended mining operations. Remaining placer gold resources at Willow Creek are estimated at 20,000 to 90,000 ounces.
At Kako, 20 miles east of Willow Creek, 30,000 ounces of placer gold was produced. At the head of Buster Creek above the Kako placer mine, rhyolite and quartz breccia crop out at the core of a gold anomaly delineated by soil sampling and trenching.
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