Is crew access allowed on the Lake Sonoma 100K course?

Yes, crew access is allowed on the Lake Sonoma 100K course. Crew are welcome at South Lake Trailhead (outbound only), Warm Springs and Liberty Glen Aid Stations. Lake Sonoma is a remote area with spotty-to-no cell service; print crew driving directions in advance and arrive with a full tank of gas.

Are drop bags allowed on the Lake Sonoma 100K course?

Yes, drop bags are allowed on the Lake Sonoma 100K course. Drop bag must be smaller than a shoe box and made of durable waterproof material, clearly labeled with runner name and bib number. Not returned to the finish until after the aid station closes; crew pickup recommended. No shipping/delivery of forgotten drop bags; available at Healdsburg Running Company Mon-Wed after the race.

Are pacers allowed on the Lake Sonoma 100K course?

No, pacers are not allowed on the Lake Sonoma 100K course.

What is the cutoff time for the Lake Sonoma 100K course?

The overall time limit for the Lake Sonoma 100K course is 19 hours from the start. Finish the 100k in less than 19 hours for a 2027 Western States qualifier.

Ultras · US · CA

Lake Sonoma 100K

2026 Lake Sonoma 100K, 50K & Trail Sisters Half Marathon

Lake Sonoma 100K · 100K

Ran · this year's race is done.

Ran as scheduled Sat Apr 11, 2026. UltraSignup's own event page for it reads 'This Event Took Place Sat. Apr 11, 2026.'

Race dateApril 11-12, 2026

Duration2 days

Start5:00am

When188 days ago

First held2008

Who's going to Lake Sonoma 100K?

I'm running itPlan your weeks and your aid station times I'm crewingWhen to leave, where to park, at every stop I'm pacing or cheeringAsk your runner for their Out Here link

Free. You can start with nothing.

Official website Results Aid stations Notify me if this race changes

Free, and always will be. NavRun makes money from race-day planning for runners who want it, never from this. Ultras change constantly, sometimes the morning of. Always confirm with the race director and the official website before you rely on anything here.

Distance 100K

Climb 15,000 ft

Descent not checked yet

High point not checked yet

Time limit 19:00:00

Aid stations 15

Started not checked yet

Finished not checked yet

Finish rate not checked yet

The course

Where it goes out and back · 15 aid stations

Western States 100 qualifying 100K. Climbs Pritchett Peak for a sunrise summit, descends to the Lake Sonoma Visitor Center, then runs an out-and-back on the original Lake Sonoma 50 Mile course to a turnaround at Lone Rock.

Not a clean out-and-back: Start -> Pritchett Peak (mile 5.8, water only) -> Woodridge (11.4) -> South Lake (12.7) is a one-way prologue never retraced; South Lake <-> Lone Rock (36.6, the turnaround) is a true out-and-back, mirrored aid-station-for-aid-station; South Lake (60.5) -> Finish (62.1) closes the route without repeating Pritchett/Woodridge. Course chart's cumulative finish mileage is 62.1 mi; the official interactive GPX map (app.racedaymap.com/lake-sonoma) measures 61.9 mi for the same route, a normal GPS-vs-chart variance.

The race

What this one is

A Western States 100 qualifying 100K, paired with a 50K and the women's Trail Sisters Half Marathon, on singletrack above Lake Sonoma in Sonoma County wine country. The 100K climbs Pritchett Peak for a sunrise summit, drops to the Lake Sonoma Visitor Center, then runs an out-and-back on the original Lake Sonoma 50 Mile course to a turnaround at Lone Rock.

Founded 2008 as the Lake Sonoma 50 Miler by John Medinger and Lisa Henson. New race directors Gina Lucrezi and Justin Keller (Trail Sisters) took over in 2022. The Trail Sisters Half Marathon was added in 2023, alongside a move of the start/finish to the Lake Sonoma Visitor Center and a cash purse for the 50 Mile. Through 2025 the spring event was still 50 Mile + Marathon + Trail Sisters Half. For the 2026 edition, a separate fall race then called the California Fall Classic 100K (also a WSER qualifier) moved to April and was rebranded the TERREX Lake Sonoma 100K; a new 50K was added; the 50 Mile and Marathon distances were dropped from the spring lineup and moved to become the 'OG LS50' inside a new October race, the Sonoma Fall Classic, run by Aravaipa Running with founder Tropical John Medinger..

Getting in

Getting in Entry, lottery and what the race asks of you before race day.

Lottery: not checked yet

Lottery opens: not checked yet

Lottery draw: not checked yet

Field cap: not checked yet

Registration: UltraSignup ultrasignup.com

Qualifying: Sub-19-hour finish qualifies for the Western States 100 (2027 lottery cycle at the time of the 2026 edition). runlakesonoma.com

Minimum age: not checked yet

Transfers: No runlakesonoma.com

Deferrals: Yes runlakesonoma.com

Running, crewing, pacing or still deciding

How NavRun helps with Lake Sonoma 100K Nineteen hours, and four stations with a clock on each.

You are running it

You reach Warm Springs, mile 24.2, before its 12:30pm cutoff, and you already knew that this morning.

An arrival time for all 13 stations, worked out from your own training.

Start free →

You are deciding

You find out Lake Sonoma 100K is months of work away, not years, and you go and get the qualifier.

Put in a race you have already run. NavRun shows you where this one sits from where you are.

No account needed →

Crew access, pacers and drop bags

The rules that shape your day Anything marked "not checked yet" is a gap in what we hold, never a no from the race.

Crew allowed: Yes runlakesonoma.com

Vehicles per runner: not checked yet

Pacers: No runlakesonoma.com

Muling: not checked yet

Drop bags: Yes runlakesonoma.com

Cupless: Yes runlakesonoma.com

Course marking: Fully Marked runlakesonoma.com

Night running: not checked yet

Dogs: not checked yet

Headphones: not checked yet

Crew rules: Crew are welcome at South Lake Trailhead (outbound only), Warm Springs and Liberty Glen Aid Stations. Lake Sonoma is a remote area with spotty-to-no cell service; print crew driving directions in advance and arrive with a full tank of gas. runlakesonoma.com

Pacer rules: Pacers are not allowed due to the difficulty of providing adequate aid. runlakesonoma.com

Drop bag rules: Drop bag must be smaller than a shoe box and made of durable waterproof material, clearly labeled with runner name and bib number. Not returned to the finish until after the aid station closes; crew pickup recommended. No shipping/delivery of forgotten drop bags; available at Healdsburg Running Company Mon-Wed after the race. runlakesonoma.com

Cutoff philosophy: Finish the 100k in less than 19 hours for a 2027 Western States qualifier. runlakesonoma.com

Aid stations

Every stop, and what you get there ● yes ○ no ? nobody has checked – does not apply to this race

Mile	Station	Cutoff	Crew access	Bag	Pacer	Med	To next
0.00	Start	?	?	?	?	?	5.80
5.80	Pritchett Peak	?	?	?	?	?	5.60
11.40	Woodridge	?	○	●	?	?	1.30
12.70	South Lake	?	●	○	?	?	4.60
17.30	Island View	?	○	○	?	?	6.90
24.20	Warm Springs	12:30pm	●	●	?	?	5.40
29.60	Wulfow	?	○	○	?	?	2.70
32.30	Liberty Glen	?	●	●	?	?	4.30
36.60	Lone Rock	4:15pm	○	?	?	?	4.30
40.90	Liberty Glen	?	●	●	?	?	2.70
43.60	Wulfow	?	○	○	?	?	5.40
49.00	Warm Springs	8:00pm	●	●	?	?	6.90
55.90	Island View	10:00pm	○	○	?	?	4.60
60.50	South Lake	?	○	○	?	?	1.60
62.10	Finish	12:00am	?	?	?	?	?

Same race, other lines

Other distances and other years

Other distances: Lake Sonoma 50K (50K)
Trail Sisters Half Marathon (Half Marathon)

Other years: 2027

What it looks like out there

Somebody has been out there with a camera the tables say the climb is long. these say what long feels like.

2 people have been out there with a camera or a microphone.

Social account

runlakesonoma (Instagram)

Social account

Run Lake Sonoma (Facebook)

Social account

These are other people's work and we link straight to them. Watching costs nothing and needs no account. More of them: every race we hold, on film.

Add to this page

What you know every one of these is read by a person before it changes anything

Ran this race? Tell the next runner what you know.

Nobody sees it until we have read it. No account, no sign-in.

Which distance? Leave blank if it applies to the whole race.

Which stop? Leave blank if it is not about one particular stop.

Give it a short title: Optional. Something like “Cal Street, mile 62 to 78”.

What do you wish someone had told you? Write it the way you would say it to someone at the start line.

Were you there? Optional, and it decides nothing. It only tells the next runner where this is coming from.

What year? Optional.

Your email: Optional, and never shown on the page. Only so we can ask you a question about this note.

Website: Leave this field blank.

See something wrong or out of date? Suggest an edit.

This changes nothing on the page on its own. Somebody checks it against the race first.

Which detail? Optional. Filled in for you when you start from a specific line on the page.

What does the page say now? Copy it as it appears, so we can find it.

What should it say? The corrected value.

How do you know? Required. Where it came from: the race email, the runner manual, what you saw on the day.

A link that shows it: Optional.

Or a photo of it: Optional. A screenshot or a photo of the sign works.

Were you there? Optional, and it decides nothing.

What year? Optional.

Your email: Optional, only so we can come back to you about this correction.

Which distance? Leave blank if it is about the whole race.

Which stop? Leave blank if it is not about one particular stop.

Website: Leave this field blank.

Seen a course preview or a film of this one? Send it over.

Somebody watches it before it goes anywhere near this page. What we are after is footage of this course, on the ground. If it would be just as true of any other race, it is not this.

What does it show that the page cannot? Required. A line is plenty. Where the climbs are, what the footing does, what the last twenty miles look like.

Were you there? Optional, and it decides nothing.

What year? Optional.

Your email: Optional, and never shown on the page. Only so we can ask you a question about this one.

Where is it? A YouTube link, a race report, a photo gallery, whatever it is.

What kind of thing is it?

Who made it? Optional, and we credit them on the page.

Website: Leave this field blank.

Have the GPX? Send us the link.

We want the address of the file the race publishes, not the file. We download it from there so the page can say where the line came from.

Are you the race director? Get in touch and we'll make it right.

We read every one of these and we write back. Every fact here carries the source it came from, and the way a wrong one gets fixed is a person checking it against what you tell us.

Where this came from. Every fact on this page records its source and when we last checked it: 97 sources for this race. Hover a source link to read the sentence it came from.

47% of what we track for a course is filled in. The rest says "not checked yet" rather than guessing.

See something wrong or out of date? Suggest an edit
Ran this race? Tell the next runner what you know
Got footage of this course? Send us the link
Are you the race director? Get in touch and we'll make it right.
Anything else: [email protected]

Ultras change. We will tell you when this one does.

Cutoffs move, races get postponed, lotteries open and close. We read the race's own sources and record where every fact came from. Put your email in and we will send you what changed, and where we read it.

No account, and nothing to cancel.

What happens to your email. Nothing else. I do not sell it, and I will not send you anything except this race changing. One click gets you out.

I keep this catalog because the information is scattered and hard to trust. Telling you when it moves is the same job.