FWP Alberton: Construction at the Cyr Bridge Fishing Access Site (FAS) boat slide is scheduled to begin Monday, July 27. Cyr Bridge is the main put-in for the Alberton Gorge whitewater section of the Clark Fork River, and the slide will remain open during daytime hours, with temporary evening closures (5 p.m.-1 a.m.) on several days, Monday-Thursday only.
The slide will be open during all daytime hours, but floaters can expect some delays and an adjustment to the launching process as portions of the wood and stairs on each side of the slide are replaced. Evening complete slide closures are anticipated for July 28-30 from 5 p.m.-1 a.m. while crews replace entire crossbeams on the slide, with the potential for a few additional evening closures during the week of August 3.
The project will ultimately replace all the wood on the slide to keep it in safe condition for boaters using the slide to launch rafts down a steep riverbank. The work is expected to take several weeks to complete. Extra Montana Fish, Wildlife & Parks and construction staff will be on hand to assist boaters with launches during the busiest times.
About The Alberton Gorge
Alberton Gorge is a roughly 9–12 mile stretch of the Clark Fork River (also called Clark’s Fork of the Columbia) in Mineral County, just west of Missoula and near the town of Alberton. It is renowned for Class II–IV whitewater, steep canyon walls, sandy beaches, ponderosa forests, and deep pools, and serves as a major put-in area (including at Cyr Bridge). Its history spans deep geological time, Indigenous presence, early exploration and settlement, the railroad era, and modern recreation/conservation.
Geological History
The canyon walls expose rocks of the Belt Supergroup, a vast package of primarily fine-grained sedimentary rocks (mudstones, siltstones, sandstones/quartzites, and some carbonates) deposited roughly 1.47–1.38 billion years ago during the Mesoproterozoic. These formed in a large intracontinental basin (linked to the breakup or rifting of the Nuna supercontinent) that filled with sediments from ancient rivers and inland seas.
Visitors can see ancient ripple marks, colorful layered rocks, and mud cracks left by long-gone shallow waters—evidence of a barren, pre-life landscape very different from today’s.
The modern gorge shape was dramatically carved during the last Ice Age. Around 15,000–12,000 years ago (estimates vary slightly by source), a lobe of the Cordilleran Ice Sheet dammed the Clark Fork River near the Idaho border, creating enormous Glacial Lake Missoula (up to 2,000 feet deep in places and covering 2,900 square miles).
The ice dam failed repeatedly (dozens of times over several thousand years), releasing catastrophic outburst floods. Water raced through the region at high speeds (tens of miles per hour), stripping soil, scouring bedrock, and shaping the steep-walled canyon, purple cliffs, and rock formations still visible today. These Missoula Floods also created the Channeled Scablands farther downstream and contributed to the Columbia River Gorge. The landscape remains wild and similar in character to how the floods left it.
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