Obsidian Cliff · Photo: USGS · Public domainLiving in Mammoth, WY: what to set up and who to call
Mammoth has no town government of its own, so Park County runs its elections and most services. Tap water in Mammoth comes from the Ynp-Mammoth Hot Springs water system, which has a clean five-year EPA record (about 22% of systems its size had a health-based violation) and a latest lead result below detection.
I’m new in town
What to set up in Mammoth, and who provides it. Tap an answer for the details and where they come from.
Power, water and internet
Who to call to start service at a new address in Mammoth.
Power comes from NorthWestern Energy
NorthWestern Energy (NorthWestern Energy LLC - (MT)), an investor-owned utility, serves all of Mammoth. Its homes paid an average of 12.4¢ per kWh in 2025, about $99 a month (its average across Wyoming).
Start or move service: northwesternenergy.com · (888) 467-2669
Service territory: HIFLD Electric Retail Service Territories (map dated Aug 2023). Prices and customers: EIA-861, 2025.
Water comes from Ynp-Mammoth Hot Springs water system
The Ynp-Mammoth Hot Springs water system supplies almost all of Mammoth. It draws surface water and serves 2,600 people in all.
No health-based violations reported to EPA in the five years to October 2026, like 78% of the 7,966 systems serving 1,001–3,300 people.
The latest lead result on file, the 90th percentile of homes sampled in Jan 2025–Dec 2027, was 0.0 ppb, below the 15 ppb action level that applied. The highest in five years was 4.0 ppb. Results below detection are reported as 0, so 0 doesn’t mean no lead at any tap.
The system’s full record: EPA ECHO report
EPA SDWIS via Envirofacts (violations pulled Oct 9, 2026) and ECHO (lead samples, 2026Q3); service area: EPA Community Water System Service Area Boundaries v3.0. Violations are counted by the start of their compliance period. WY5680092.
Which providers serve Mammoth
This card will list the home internet providers the FCC’s National Broadband Map shows in Mammoth, the share of addresses that can get 100/20 Mbps and the share with fiber, with the map’s “as of” date.
Source to come: FCC Broadband Data Collection.
We don’t have Mammoth’s trash rules yet
Pickup rules, the dump and recycling in Mammoth.
No town hall: the county runs things
Mammoth is unincorporated, so Park County is the local government.
Election office: FVAP local election office directory, updated Dec 2023; jurisdictions: EAC EAVS 2024. Registration rules and links: vote.gov, updated Nov 18, 2024.
Mammoth is in ZIP code 82190
ZIP codes where Mammoth residents live, with the share of the town in each.
| ZIP | Post office name | Share of Mammoth | ZIP’s residents in Mammoth |
|---|---|---|---|
| 82190 | Yellowstone National Park, WY | 100% | 67% |
Census 2020 ZIP Code Tabulation Areas, by census block; post office names: GeoNames (CC BY 4.0). ZIPs created since 2020 are missing.
Getting around, the ER and the library
One line each; the subject pages have the rest.
ER: CMS hospital data. Library: IMLS Public Libraries Survey, FY2024.
Questions about living in Mammoth
Who supplies Mammoth’s drinking water, and has it had violations?
The Ynp-Mammoth Hot Springs water system (EPA ID WY5680092). It reported no health-based violations to EPA in the five years to October 2026; 78% of systems its size had none. Its latest lead 90th percentile was 0.0 ppb (Jan 2025–Dec 2027), against a 15 ppb action level.
Who provides electricity in Mammoth?
NorthWestern Energy (NorthWestern Energy LLC - (MT)), an investor-owned utility. Its homes paid about 12.4¢ per kWh in 2025 (EIA).
What ZIP codes are in Mammoth?
82190. Census 2020 ZIP Code Tabulation Areas.
How do I register to vote in Mammoth?
Wyoming has no online registration; you can register in person up to and including Election Day or by mail (received 14 days before). Elections here are run by the Park County Clerk. Check your registration at sos.wyo.gov.
Sources & dates
Every answer above names its source. Here they are with their dates.
- Water: EPA SDWIS (Envirofacts, pulled Oct 9, 2026), ECHO SDWA 2026Q3, EPA CWS Service Area Boundaries v3.0.
- Power: HIFLD Electric Retail Service Territories (map Aug 2023); EIA-861 final 2025.
- Trash: OpenStreetMap, Geofabrik extract of Oct 9, 2026. © OpenStreetMap contributors (ODbL).
- ZIP codes: Census 2020 ZCTA relationship files; GeoNames postal codes (CC BY 4.0).
- Schools: NCES Common Core of Data, 2024–25.
- Registration: vote.gov, updated Nov 18, 2024 (read Oct 10, 2026). Official sites and area codes: Wikidata.
- Election office: FVAP local election office directory (fetched Oct 10, 2026; each record dated), EAC EAVS 2024 jurisdictions; registration and lookup links from vote.gov’s state data, checked Oct 10, 2026.
- Internet (FCC): pending.