·7 min read·Vegeta — RiverScout Editorial

The Au Sable River: Michigan's Canoe Marathon Corridor and Trout-Water Heritage

Au Sable River →

The Au Sable River: Michigan's Canoe Marathon Corridor and Trout-Water Heritage

Flowing approximately 140 miles from its headwaters near Grayling to its mouth on Lake Huron at Oscoda, the Au Sable is one of the most storied paddling and angling rivers in the Midwest. Each July the river hosts the AuSable River Canoe Marathon, a 120-mile overnight test from Grayling to Oscoda that ranks among the longest and oldest nonstop canoe races in North America. The rest of the year the same waterway is a celebrated trout stream, a Michigan Natural River, and the birthplace of Trout Unlimited. For anyone planning to fish, paddle, or just understand northern Michigan river culture, the Au Sable is the reference point.

Geography and length

The Au Sable drains much of the northern Lower Peninsula, rising in the spring-fed plains of Crawford County and flowing generally east across the Huron-Manistee National Forests before turning north to Lake Huron at Oscoda. Total length is approximately 140 miles, with the main stem passing through both the South Branch confluence and the Au Sable's signature series of hydroelectric impoundments — Mio, Alcona, Loud, Five Channels, Cooke, and Foote dams — each backed by a deep pond that the marathon's overnight leaders negotiate just before dawn (Michigan Department of Natural Resources — Au Sable Natural River Plan).

Real-time flow on the main stem is tracked at the principal USGS gauge, USGS 04137500, which measures discharge and stage near the lower river. Paddlers planning a recreational trip and anglers chasing hatches consult the same gauge the marathon's organizers use to set the annual course condition. The river's gradient averages roughly four feet per mile on the main stem — slow, steady, and forgiving for tripping canoes, kayaks, and drift boats. Trip planning resources and current flow are available on the RiverScout Au Sable River page.

History

The Au Sable watershed's modern character was forged, and scarred, by timber. From the 1830s through the 1920s, the Au Sable watershed was logged to feed the regional timber industry of 1850 to 1910 and the railroad expansion of 1860 to 1910. Local sawmills, logging drives, and downstream lumber operations were the major operators. The end came in stages: the old-growth stands were exhausted by 1910, state forestry conservation began in 1915, and the establishment of state forests in the 1930s closed the book on large-scale logging (Regional State Historical Society; Michigan Department of Natural Resources).

It was the fishing that made the Au Sable famous. In 1959 it became the birthplace of Trout Unlimited, and the coldwater ethic that organization championed still defines the river. The AuSable River Canoe Marathon, run each July since 1947, added a second identity — a 120-mile nonstop test that ties Grayling to the Lake Huron mouth in a single grueling night-and-day push. Recognition followed the reputation: the river is protected under the Michigan Natural Rivers program and is widely recognized as one of Michigan's signature conservation watersheds.

Today the river is managed as much as it is paddled. Since 2010, the regional DNR and local watershed partnerships have worked to undo a hundred years of damage, with streambank stabilization from 2015 to 2024, native fish restocking from 2017 to 2024, a nutrient reduction strategy implemented between 2018 and 2024, and water-quality gains from 2020 to 2024. Trout Unlimited's 2024 lunker-structure habitat work and a 2023 climate-change assessment produced with Michigan State University continue that effort (Trout Unlimited — Protecting the Au Sable; Michigan State University Extension — Climate Change Assessment).

The AuSable River Canoe Marathon

Founded in 1947 and run every July since, the AuSable River Canoe Marathon is a 120-mile overnight race from Grayling to Oscoda. Boats launch at 9:00 PM on Saturday and race through the night and the following day, with leaders reaching Oscoda the next morning. The full course passes through sixteen timed checkpoints, including six dam-portage stops at Mio, Alcona, Loud, Five Channels, Cooke, and Foote dams, where teams carry their canoes around each structure. The six dams come in roughly two clusters: Mio is the first portage, hit around midnight; Alcona, Loud, and Five Channels come between 3 AM and dawn; and Cooke and Foote are morning checkpoints as the leaders approach Oscoda.

The 2025 marathon, the most recent completed at the time of writing, had 115 boats on the line. 102 teams officially finished; the remaining 13 crews dropped out across the night, with the highest dropout counts at Camp Ten Bridge (checkpoint 6), McKinley Bridge (checkpoint 8), 4001 Bridge (checkpoint 9), and Loud Dam (checkpoint 11) — the late-night stretches between the dam portages. The 2025 winning team was #99 Travis Mecklenburg and Weston Willoughby, finishing in 14:17:07 elapsed, followed by #13 Chris Issendorf and Christophe Proulx (14:20:43) and #98 Wesley Dean and Logan Mynar (14:31:23). The full final finisher crossed Oscoda at 18:59:53 elapsed.

The next marathon is scheduled for 9:00 PM Eastern on Saturday, July 25, 2026. During the race window (start minus 2 hours through start plus 26 hours) the marathon's RiverScout replay tab flips into live mode and refreshes every 60 seconds with official checkpoint splits. Registration, race rules, and current-year results are at ausablecanoemarathon.org, the race's official site.

Fishing and the coldwater heritage

The Au Sable's modern reputation as a trout stream dates to the mid-twentieth century, and the 1959 founding of Trout Unlimited on the river codified the conservation ethic that has protected it since. Cold spring-fed water stays below 65°F through the summer, sustaining wild brown trout, rainbow trout, and brook trout populations across the main stem and its tributaries. Spring and early-summer hatches — Hendricksons typically in April and early May, March Browns in late May, and Sulphurs running through June — give way to a long Hexagenia (Hex) window from late June through July, the same window the marathon's overnight paddlers race through (Michigan DNR — Trout Fishing on the Au Sable).

Access points for anglers are largely shared with paddlers, with the river's bridges and public launches offering walk-in or car-top access across the corridor. Drift boats are common on the lower river; wading anglers work the same riffles and pools that the marathon's overnight racers see in the dark. Grayling-area fly shops (and others along the corridor) provide current conditions, hatch reports, and guide services for visiting anglers.

Paddling the Au Sable outside race week

Outside the marathon's single overnight in late July, the Au Sable is a quiet, multi-day tripping river — one of the best in the Midwest for paddlers who want a longer float with car-supported resupply or a fully-wilderness experience. Three trip sections are common:

  • Grayling to Mio — about 50 miles, popular family float. Multiple days of mellow water, with the small towns of Grayling and Mio offering resupply and take-outs. Good for first-time Au Sable paddlers and anglers who want a longer float with easy access.
  • Mio to Oscoda — about 70 miles, multi-day tripping. The marquee recreational section, passing through five of the marathon's six dam-portage checkpoints — Alcona, Loud, Five Channels, Cooke, and Foote (Mio is the divider between the upper and lower trips). Strong paddlers can run it in three to four days; trip boats commonly take a week or longer.
  • The South Branch — about 40 miles, solitary and wild. The Au Sable's least-paddled section, threading the state forest south of the main stem and rising out of Lake St. Helen. Protected from new dams under the broader state forest framework but not formally designated as a Michigan Natural River in its own right.

Trip length and difficulty scale with the section. Campgrounds and primitive campsites exist at most bridges and several intermediate access points; Grayling-based Carlisle Canoe Livery and Penrod's Au Sable handle rentals, shuttles, and put-ins for visiting paddlers. Real-time flow on the principal gauge (USGS 04137500) is available on the RiverScout Au Sable River page, along with the access-point map, the 10-year flow pattern, and current stocking and hatch data.

The Au Sable as a year-round river

The Au Sable is at its busiest for a single overnight each July, when the marathon pulls a hundred-plus boats through the corridor between sunset and the following noon. For the other 364 days the river runs quiet — drift boats and wading anglers in spring and fall, tripping families and overnight paddlers in summer before and after race week, and a hardier cohort of steelhead anglers in the cold months around the Lake Huron mouth.

What ties the river together across all of those uses is the same thing that has drawn people to it for well over a century: cold, clear, spring-fed water; a corridor that runs from the pines of the Huron-Manistee National Forests to Lake Huron; and a fishing-and-paddling culture that treats the river as something worth protecting. The 1947 marathon and the 1959 founding of Trout Unlimited crystallized that culture into organizations and events that have shaped the river's modern conservation, building on earlier state forestry and natural rivers work.