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Sagebrush hills rising above a tree-lined fairway at the Sun Valley golf course
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The Big Lost (Rebecca's Private Idaho) course maps

Gravel out of Sun Valley over Trail Creek Summit and into the Big Lost River country, from the 19 mile Tater Tot to the 118 mile Fully Loaded.

September 8 to 11, 2027 Ketchum and Sun Valley, Idaho

The Big Lost is the gravel race that ran for 14 years as Rebecca's Private Idaho. Rebecca Rusch started it in 2013, and it has been held every year since in the backcountry behind Ketchum and Sun Valley. After the 2026 edition the organizer, Bike Monkey, renamed it for the Big Lost River, which runs beside the course in Copper Basin and at Wildhorse before it sinks into the ground past Arco.

The main event is on Saturday at Champions Meadow in Sun Valley, with four routes named for potatoes. All but the Tater Tot climb over Trail Creek Summit and drop to the far side. The optional stage race adds two days before it: the Harriman Trail on Wednesday and the Dollarhide Summit hill climb on Thursday.

The map shows the 2026 routes, since the 2027 ones aren't out yet. The organizer says cell service is severely limited or missing almost everywhere on the courses outside town, so download the map before you go. GPS still shows where you are with no signal.

This is an unofficial guide: Goat Maps isn't affiliated with The Big Lost. Check the official site before you enter or race.

The Big Lost course map

Every course's aid stations on the Goat Maps topo map. Each course has a map of its own further down.

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The Big Lost courses

CourseDistanceClimbingStartTime limit
Fully Loaded118 mi (190 km)7,081 ft (2,158 m)
Baked Potato104 mi (167 km)6,281 ft (1,914 m)
French Fry57 mi (92 km)3,644 ft (1,111 m)
Tater Tot19 mi (31 km)1,209 ft (369 m)

The Big Lost Fully Loaded

The whole Baked Potato with the original Copper Basin loop added on.

Distance
118 mi (190 km)
Climbing
7,081 ft (2,158 m)

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New in 2026, the Fully Loaded rode everything the Baked Potato did and added the Copper Basin loop, about 18 miles and 1,000 feet of climbing, after the Big Lost rest stop. It started at 7:30 AM in 2026, with the Baked Potato.

The 2026 rider guide set three time cuts. The first was at mile 22, near Wildhorse: miss 9:45 AM and you were sent onto the French Fry. If you weren't at the Copper Basin cut, just before the Big Lost rest stop at mile 61, by 1:00 PM, you finished on the Baked Potato instead. El Diablito, 5.5 miles and about 600 feet of rough climbing, closed at 3:00 PM at mile 96.5, and the rider guide expected that one to catch as much as 15% of the Fully Loaded riders still out there.

A dirt road through tall grass and pines below a rocky peak
Chris Kofoed / Unsplash

The Big Lost Baked Potato

The flagship, rebuilt for 2026 with a 2,500 foot climb over Corral Creek Summit.

Distance
104 mi (167 km)
Climbing
6,281 ft (1,914 m)

Take this course offline

Download its map in Goat Maps and you can find the next aid station without a signal.

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The 2026 Baked Potato went over Trail Creek Summit, with a rest stop at the top at mile 12, and on into the Big Lost country. At mile 46.6 the Burma Road rest stop sat at the bottom of the day's big climb: 6 miles and 2,500 feet up to Corral Creek Summit, around 8,700 feet. Fill up there. The Big Lost stop was at mile 62 and Copper Basin at 65, and Burma Road, Big Lost and Copper Basin all had bottle feeds.

Two cuts applied in 2026. Riders not at mile 22 by 9:45 AM went onto the French Fry, and the organizer estimated that would be the slowest 10% of the field. At mile 82 the cut was 3:00 PM; miss it and you rode straight past El Diablito. Hand cyclists and recumbents skip El Diablito anyway and stay on Trail Creek Road.

The Big Lost French Fry

Trail Creek Summit and the Wildhorse country without the full day.

Distance
57 mi (92 km)
Climbing
3,644 ft (1,111 m)

Take this course offline

Download its map in Goat Maps and you can find the next aid station without a signal.

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The French Fry climbs Trail Creek Summit like the long routes, with the same washboards and headwinds the organizer warns about, then loops back past Wildhorse. In 2026 you passed the Trail Creek rest stop at miles 12 and 45, and the Wildhorse one at 24 and 32.

It had no time cuts in 2026 and started at 8:00 AM.

A wide valley near Sun Valley seen from a sagebrush slope, with ski runs on the peak at left
Emily Barber / Unsplash

The Big Lost Tater Tot

Nineteen miles, half pavement and half gravel up Corral Creek Road and back.

Distance
19 mi (31 km)
Climbing
1,209 ft (369 m)

Take this course offline

Download its map in Goat Maps and you can find the next aid station without a signal.

Open in web map

The Tater Tot starts and finishes on pavement, with the gentle climbs and swoopy gravel of Corral Creek Road in the middle. In 2026 its rest stop was the turnaround at mile 8.5. It had no time cuts and started last of the four, at 8:30 AM.

Registration and the stage race

Registration for 2027 wasn't open when this page was checked. It stays open until the event sells out; if there's room on the day you can still sign up in person, at a higher price. Changes of distance and transfers to a friend go by email to the organizer, by August 15.

In 2026 the Saturday routes cost $50 for the Tater Tot, $200 for the French Fry, $250 for the Baked Potato and $285 for the Fully Loaded. Juniors under 18 rode Saturday free and paid half for the other two stages. Veterans got 15% off, and groups of three or more up to 20%.

The stage race adds the Harriman on Wednesday, 35 miles and 2,599 feet of singletrack and doubletrack below the Boulder Mountains from Baker Creek, and the Dollarhide on Thursday, a 50 mile ride from Ketchum with a 4.5 mile timed climb to Dollarhide Summit. You can ride one, two or all three stages, and in the full stage race you have to ride the same frame every day. Don't ride Highway 75 to or from Baker Creek: that gets you disqualified.

Getting to Sun Valley

A wide valley near Sun Valley seen from a sagebrush slope, with ski runs on the peak at left
Emily Barber / Unsplash

The nearest airport is Hailey's (SUN), 11 miles south of Ketchum, with flights from Salt Lake City, Seattle, San Francisco and Los Angeles. Boise is about two and a half hours' drive away, with more flights.

Champions Meadow is on Sun Valley Road between Spruce and Dollar, and the organizer asks you to ride there: Ketchum is small and a bike path runs to the start. If you have to drive, the event lot is on Dollar Road, entered from Saddle Road. Don't leave the car in a two-hour spot in town, and RVs can't park inside Ketchum. There's dispersed camping off almost every dirt road around the valley, mostly out of cell range, but finding a spot can take some driving.

Support on course

A dirt road through tall grass and pines below a rocky peak
Chris Kofoed / Unsplash

There is no personal support. Bottle hand-ups from friends and stashed bottles get you disqualified, so you ride from rest stop to rest stop. Each has water, some food, restrooms and shade. The roads stay open to traffic, and the organizer asks families not to drive the course to cheer. It's open range too, so expect livestock, and leave gates the way you find them.

Timing stops 2.75 miles before town. Roll through the finish flags there to get your time, then ride back to the festival. Leave a bag with your rider number at the bag drop that morning and your dry clothes will be waiting.

Weather and smoke

Ketchum averages a high of 69°F and a low of 36°F in September, by NOAA's 1991 to 2020 normals, and the summits on course are much higher than town. In race week of 2026 the organizer warned of frost on Wednesday morning at Baker Creek, which usually runs 5 to 10 degrees colder than Ketchum.

Wildfire smoke is the bigger worry. The organizer cancels or postpones a stage when the air quality is unsafe, as it did with Stage 1 in 2024, and it doesn't refund when that happens.

The Big Lost aid stations and GPS coordinates

For crews and spectators: each place on the map in decimal degrees, latitude first. Paste them into any map app or add them as waypoints in Goat Maps.

  • Champions Meadow (start and finish)

    5,879 ft (1,792 m)

    43.68578, -114.35912

  • Trail Creek (top of the climb)

    7,900 ft (2,408 m)

    43.82517, -114.26277

  • Wildhorse

    7,051 ft (2,149 m)

    43.89919, -114.10116

  • Burma Road

    6,230 ft (1,899 m)

    43.96791, -113.80352

  • Corral Creek Summit

    8,720 ft (2,658 m)

    43.90480, -113.79484

  • Big Lost

    7,776 ft (2,370 m)

    43.82364, -113.84967

  • Copper Basin

    7,497 ft (2,285 m)

    43.86175, -113.90368

  • Tater Tot turnaround

    6,949 ft (2,118 m)

    43.73940, -114.23230

The Big Lost FAQ

When is The Big Lost 2027?

September 8 to 11, 2027, Wednesday to Saturday. The main event, with all four potato routes, is on the Saturday, September 11. The map shows the 2026 routes; the 2027 courses and start times aren't out yet.

Is The Big Lost the same race as Rebecca's Private Idaho?

Yes. Rebecca's Private Idaho ran from 2013 to 2026, and the organizer renamed it The Big Lost after the 2026 edition. Bike Monkey still runs it.

What are the time cuts on the Baked Potato and Fully Loaded?

In 2026: mile 22 by 9:45 AM, or you switched to the French Fry. Fully Loaded riders also had to reach mile 61 by 1:00 PM or finish on the Baked Potato. El Diablito closed at 3:00 PM, at mile 82 on the Baked Potato and 96.5 on the Fully Loaded. The French Fry and Tater Tot had no cuts. Those times are the 2026 rider guide's. The race site's FAQ gave 9:15 AM for the first cut, and the organizer's course map marked the Copper Basin one 1:30 PM, so check the 2027 guide when it comes out.

Can friends hand me bottles on the course?

No. Personal on-course support isn't allowed, including bottle hand-ups and stashed bottles. Carry what you need between the race's rest stops. Friends who want to help can volunteer at one.

Is there cell service on The Big Lost course?

Barely. The organizer says it's severely limited or missing almost everywhere outside town. Download the map in Goat Maps before you go: your phone's GPS still shows where you are with no signal.

Can I ride The Big Lost on a mountain bike?

Yes, and many riders do. The organizer suggests narrower tires with little tread, around 1.8 inches. Sturtevants in Sun Valley rents gravel bikes if you book early.

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Updated . An unofficial guide, from the organizer's published information. Coordinates from the organizer's course and OpenStreetMap contributors. Photos from Unsplash. Organize a race? We help with course files.