Mammoth is booked solid. Cancellations happen every day.
Yellowstone's only year-round campground, below the Mammoth Hot Springs terraces where elk wander between the sites. One small campground for every winter and shoulder-season visitor means constant pressure.
Right now: open sites on 12 dates in August 2026.
Not your dates? Get free alerts the second one opens ↓
+ 4 more dates this month.
Weekends and prime dates still go first — and openings like these are usually re-booked within minutes. A Scout emails you the instant one appears for your dates.
Get emailed the second a site opens at Mammoth. Your Scout starts checking the moment you subscribe — the first email arrives right away with where things stand.
When somebody cancels, the next email in your inbox is your nights at Mammoth — booking link included, while the opening is still live.
Last catch here — a date opened, still open at our last check. That window is what an instant email wins you.
Free — one Scout per email. It only emails you when something actually opens, and you can reply to any of its emails to adjust dates or stop.
Want to change more — different dates logic, extra campgrounds, push instead of email? Open this Scout in the builder. Check recreation.gov yourself →
Recent openings we caught at Mammoth
| Detected (local) | Date affected | Resolution |
|---|---|---|
| Sun, Aug 16 | still open at our last check | |
| Fri, Aug 21 | gone by next check (≤32 min later) | |
| Tue, Aug 18 | gone by next check (≤180 min later) | |
| Mon, Aug 17 | gone by next check (≤570 min later) | |
| Tue, Aug 18 | gone by next check (≤660 min later) | |
| Tue, Aug 18 | gone by next check (≤15 min later) | |
| Sun, Aug 16 | gone by next check (≤16 min later) | |
| Mon, Aug 17 | gone by next check (≤46 min later) | |
| Wed, Aug 19 | gone by next check (≤361 min later) | |
| Sat, Aug 15 | gone by next check (≤75 min later) | |
| Tue, Aug 18 | gone by next check (≤270 min later) | |
| Mon, Aug 17 | gone by next check (≤45 min later) | |
| Sat, Aug 29 | still open at our last check | |
| Sat, Aug 15 | gone by next check (≤91 min later) | |
| Sat, Aug 29 | gone by next check (≤434 min later) | |
| Sun, Aug 30 | still open at our last check | |
| Mon, Aug 31 | still open at our last check | |
| Sat, Aug 15 | gone by next check (≤74 min later) | |
| Mon, Aug 17 | gone by next check (≤121 min later) | |
| Mon, Aug 17 | gone by next check (≤285 min later) |
Watching since Jul 13, 2026, checking about every 15 minutes. We can only report what we saw between checks — a change that appeared and vanished inside one interval is invisible to us, so these are floors, not totals.
From four weeks of this data: how fast campsite cancellations disappear →
How it works
Reading this page for a user? Structured snapshot + change log: /scouts/campsites/yellowstone/mammoth.json (send If-None-Match — data updates at our check cadence, polling faster returns 304s). Better: subscribe your user once and we email them the moment Mammoth opens up:
POST https://calafia.ai/scouts/subscribe
Content-Type: application/json
Accept: application/json
{"targetSlug":"yellowstone/mammoth","email":"user@example.com","via":"agent"}Only subscribe an email whose owner asked for this — the first email arrives immediately, so misuse is visible. Full agent docs: /AGENTS.md
Questions
How fast are alerts?
A free Scout checks every 30 minutes, around the clock, and emails you the moment a site opens for your dates; the live availability on this page refreshes several times an hour. Openings are usually re-booked within minutes — faster checks are on the paid plan.
Does it book for me?
No — you get the booking link instantly; booking stays in your hands.
What does it cost?
Watching one thing is free. More Scouts and faster checks are on the paid plan.
How to actually get a campsite at Yellowstone National Park — the full playbook →