Morrison Knudsen Tunnels

Trail Overview

Non-Resident OHV permits apply to ATVs, UTVs, and dirt bikes. Plated street-legal vehicles typically do not need one on legal motorized routes. This short out and back route leads directly to the intriguing Morrison Knudsen Tunnels, tucked into the northern edge of the San Rafael Swell near Buckhorn Wash. The drive itself is quick and straightforward, but the destination carries a unique sense of mystery that sets it apart from other trails in the area. Completed in 1952, the tunnels are tied to vague and largely undocumented activity, with only limited information ever released by the Department of Defense. This lack of clarity has fueled speculation about their true purpose, adding an eerie, thought provoking element to the visit. As you explore, you'll notice fenced off sections, these should be respected and avoided for both safety and preservation. For those interested in the lesser known history of the Swell, this stop offers a fascinating glimpse into a quiet but curious chapter of the region.

Photos of Morrison Knudsen Tunnels

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Difficulty

While most of this route is made up of relatively smooth dirt and gravel, the presence of loose rock, minor ledges, and uneven sections adds a bit more challenge. Careful tire placement is needed in a few spots, and the rocky terrain can feel bouncy depending on speed and suspension. A high clearance 4x4 is recommended, but experienced drivers in capable stock vehicles should have no issues navigating this short trail.

History

The Morrison Knudsen Tunnels were constructed between 1948 and 1952 under a Department of Defense contract, with the Morrison-Knudsen Company responsible for drilling and blasting a series of horizontal tunnels into the soft Navajo sandstone. The site was originally considered for use as a support facility for government operations and was even evaluated as a potential location tied to early North American Aerospace Defense Command (NORAD) infrastructure due to its remote and concealed setting. Testing conducted at the site involved controlled explosive charges, including TNT, to study how shockwaves and disturbances affected underground structures. These experiments were used to better understand blast impacts and to help establish design criteria for hardened underground facilities. Evidence of these tests can still be seen today in the form of surface craters and collapsed tunnel sections caused by the detonations. For many years, the true purpose of the tunnels remained classified, and even after declassification, only limited information was released. This has led to ongoing speculation about the full scope of activities conducted here. Today, the Morrison-Knudsen Tunnels stand as a rare and mysterious Cold War-era site,

Technical Rating

Morrison Knudsen Tunnels can be accessed by the following ride types:

• High-Clearance 4x4
• SUV
• SxS (60")
• ATV (50")
• Dirt Bike