Billionaire Oxbow Carbon founder and renowned collector William “Bill” Koch is letting the market dictate the final gavel on his legendary Castle Creek Valley kingdom, sending his sprawling 52.2-acre “Elk Mountain Lodge” compound to a highly anticipated 10-day auction this July. The America’s Cup winner and oil dynasty heir is deploying a sophisticated exit strategy after initially rolling out the irreplaceable Rocky Mountain retreat with a record-shattering $125 million price tag in early 2025, later shaving $26 million off the ask to test the waters at $99 million. Rather than chasing traditional buyers in a cooling ultra-luxury mountain market, Koch—who has famously utilized the auction format to trade multi-million-dollar masterworks of art and vintage wine—is partnering with Concierge Auctions and listing agent Steven Shane of Compass to trigger a global bidding war starting July 7, offered with no reserve beyond the opening bid.
The monumental real estate asset represents a generational masterwork that took years to meticulously assemble. Koch originally captured the core parcel—a historic 1930s dude ranch and beloved local wedding venue—in 2007 for $26.5 million, systematically acquiring additional buffer acreage before strategically partitioning and offloading a 31-acre parcel for $14.5 million in 2020. What remains is a completely unduplicatable, low-density wilderness enclave spanning 25,277 square feet of ultra-premium, log-and-stone living space across eight separate structures.
A masterpiece of mountain architecture
The crown jewel of the compound is a magnificent, 16,631-square-foot main lodge custom-reimagined by award-winning Colorado architecture firm Rowland+Broughton to blend rugged frontier-inspired architecture with high-end modern sustainability. Perfect for massive family gatherings or hosting on an elite scale, the estate boasts a total of 15 bedrooms and 19 bathrooms distributed across the main residence and seven authentically crafted guest cabins—one of which has been fully converted into a state-of-the-art fitness center and wellness suite. The pristine alpine acreage delivers an unparalleled backcountry playground, featuring sweeping panoramas of the majestic Elk Mountain Range, two tranquil private ponds, extensive trout-rich river frontage, private hiking and cross-country ski trails, and an expansive eight-car garage built for an elite vehicle collection, all situated just 11 miles south of the world-class dining, culture, and ski slopes of downtown Aspen.
An elegant 20-seat dining room provides the perfect setting for lavish dinners, while a climate-controlled wine cellar ensures that every bottle is preserved at the perfect temperature. Additional highlights of the main residence include two studies, a screening room that doubles as an altitude-acclimation chamber, and expansive floor-to-ceiling windows that frame breathtaking mountain views.
Adding to the estate’s accommodations are seven guest cabins, bringing the total living space to nearly 25,300 square feet, with 14 bedrooms and 17 bathrooms. One of the cabins is currently used as a state-of-the-art gym, while others serve as private retreats for family and guests.
An outdoor playground in the heart of Aspen
The estate is designed for outdoor enthusiasts, offering an array of recreational amenities that make the most of its Rocky Mountain setting. The property features two hot tubs, private ponds, and miles of scenic hiking and cross-country skiing trails, providing year-round opportunities for adventure.
Nestled along Rooney Circle, a private road named after Koch’s wife Bridget Rooney Koch, the estate offers unmatched privacy while remaining close to the world-class restaurants, luxury shopping, and cultural experiences that Aspen has to offer.
A legacy property with global appeal
Bill Koch, a member of the ultra-wealthy Koch family and founder of Oxbow Carbon Corporation, is no stranger to high-end real estate. In addition to Elk Mountain Lodge, he owns properties in New York City, Palm Beach, and Cape Cod. He is also the owner of Bear Ranch, a 4,500-acre estate in Paonia, Colorado, where he has meticulously created a replica of an Old West town, demonstrating his passion for history and preservation.
Koch’s decision to list Elk Mountain Lodge comes as he and his wife transition into a new phase of life, now that their children have grown. Recognizing the strength of the Aspen luxury real estate market, where median sale prices have skyrocketed from $4.95 million in 2016 to $13.23 million in 2024, he sees this as the perfect time to pass the estate on to its next steward.
An exclusive opportunity to own a slice of Aspen’s elite landscape
With its unparalleled natural beauty, expansive living spaces, and unmatched amenities, Elk Mountain Lodge is more than just a home—it’s a legacy estate. Whether as a private mountain retreat, a family compound, or a trophy property, this Aspen masterpiece stands as a once-in-a-generation opportunity for a buyer looking to secure a luxurious escape in one of the world’s most coveted destinations.
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