Hot springs range from natural thermal-spring localities and Yellowstone’s hydrothermal features to geothermal direct-use systems and clinical hydrotherapy. The statistics below keep those measurements separate by geography, period, population, and evidence type.
Key Hot Springs Statistics
The most useful headline figures span natural resources, tourism, geothermal infrastructure, and selected clinical studies:
- More than 1,000 thermal-spring localities were catalogued in the United States in the 1937 USGS inventory.
- Idaho, California, and Nevada each had more than 150 thermal-spring localities in the 1937 catalog.
- Wyoming had more than 100 hot-spring localities in the 1937 catalog.
- Yellowstone contained more than 10,000 hydrothermal features in the dynamic inventory reported in 2025.
- Yellowstone’s thermal features were grouped into about 120 thermal areas and thermal water bodies in the 2025 report.
- About 1,000 active geysers existed worldwide according to the estimate reported by USGS in 2025.
- Yellowstone recorded 4,744,353 recreation visits in calendar year 2024.
- Yellowstone recorded 4,501,382 recreation visits in calendar year 2023.
- Yellowstone recorded 3,290,242 recreation visits in calendar year 2022, when historic flooding disrupted access.
- July 2024 brought 992,352 recreation visits to Yellowstone National Park.
- Fall accounted for about 21% of Yellowstone’s annual park-wide use in the NPS overview reported in 2025.
- Winter visitation at Yellowstone had never exceeded 6% of annual park-wide use in the historical overview through 2025.
- U.S. installed geothermal power capacity was approximately 3.673 GW in 2020.
- More than 1.7 million U.S. geothermal heat-pump units had been installed according to the 2020 DOE report.
- U.S. geothermal direct-use installed capacity was 485 MWth in the 2020 report.
- DOE estimated U.S. direct-use potential at 231 GW by 2050.
- Pooled pain improvement in chronic-low-back-pain hot-spring hydrotherapy trials was SMD −0.901, with a 95% CI of −1.777 to −0.025.
- Pooled quality-of-life improvement was SMD 0.104, with a 95% CI of −0.397 to 0.606.
- A Hungarian trial used 42°C thermal-mineral water for 15 sessions over 3 weeks.
Contents
- U.S. thermal-spring footprint statistics
- Yellowstone hydrothermal feature data
- Hot springs visitation and tourism trends
- Geothermal direct-use and energy statistics
- Hot spring hydrotherapy pain and function statistics
- Treatment, quality-of-life, and safety evidence
U.S. Thermal-Spring Footprint Statistics
The USGS inventory, published for the 1937 catalog, provides a historical baseline rather than a current census. It counted thermal-spring localities, not visitor facilities, bathing pools, or all geothermal features.
| Geography | Historical count | Period and definition |
|---|---|---|
| United States | More than 1,000 localities | 1937 USGS thermal-spring catalog |
| Idaho | More than 150 localities | 1937 catalog |
| California | More than 150 localities | 1937 catalog |
| Nevada | More than 150 localities | 1937 catalog |
| Wyoming | More than 100 localities | 1937 catalog |
The 1937 catalog also shows how recorded coverage expanded over time. The historical USGS list began with 21 spring localities in an 1831 physician’s book and reached 181 listed localities in its 1855 edition; those figures reflect the books’ coverage, not every spring in existence.
Source: Thermal springs in the United States (USGS). The state and national counts are historical inventory figures and should not be read as current totals.
Yellowstone Hydrothermal Feature Statistics
Yellowstone illustrates why “hot springs” can mean different things statistically. The park’s dynamic inventory includes hot springs, geysers, mud pots, and fumaroles, while thermal areas and water bodies are broader groupings.
- The 2025 USGS report counted more than 10,000 hydrothermal features in Yellowstone National Park, excluding some underwater features and recognizing that features can appear and disappear.
- Those features were clustered into about 120 distinct thermal areas and thermal water bodies, an approximate grouping rather than a count of individual springs.
- USGS reported an estimate of about 1,000 active geysers worldwide in 2025; geyser activity can change over time.
- A cited 2008 inventory recorded at least 700 Yellowstone geysers, including dormant geysers, and described at least 500 as actively erupting under that inventory’s definitions.
- Steamboat Geyser’s reported eruption height was 70–120 meters in the 2018 reference; this is a geyser measurement, not a hot-spring count.
Source: Yellowstone’s thermal areas, by the numbers (USGS Yellowstone Volcano Observatory). The geyser inventory is older than the 2025 report and is not directly comparable with the dynamic feature estimate.
Hot Springs Visitation and Tourism Trends
Yellowstone visitation is a useful access and tourism proxy, but the National Park Service counts recreation visits across the park. These figures do not measure attendance at individual hot springs.
| Year | Yellowstone recreation visits | Measurement note |
|---|---|---|
| 2018 | 4,115,000 | Annual park-wide visits |
| 2019 | 4,020,288 | Annual park-wide visits |
| 2020 | 3,806,306 | COVID-related closure affected access |
| 2021 | 4,860,242 | Annual park-wide visits |
| 2022 | 3,290,242 | Historic flood disrupted access |
| 2023 | 4,501,382 | Annual park-wide visits |
| 2024 | 4,744,353 | Annual park-wide visits |
The NPS fact sheet described 2024 visitation as 44% above 2022, while attributing part of the comparison to the 2022 flood-related access disruption. The percentage is rounded and remains a park-wide comparison.
Monthly figures show the scale of peak-season use without converting it into hot-spring attendance:
- Yellowstone recorded 992,352 recreation visits in July 2024 and 969,692 in July 2023.
- July 2021 recorded 1,080,767 recreation visits, while July 2025 recorded 975,109.
- Fall represented about 21% of annual Yellowstone use in the 2025 overview, while winter had never represented more than 6% of annual use in the historical overview through 2025.
- The cited visitor-origin profile reported North American visitors at 77%, European visitors at 13%, and Asian visitors at 8%; these are visitor-profile shares, not hot-spring-user shares, and may vary by year.
Sources: Recreation Visits by Month: Yellowstone National Park and Yellowstone National Park Resources & Issues 2023 Front (NPS).
Geothermal Direct-Use and Energy Statistics
Energy statistics provide context for geothermal resources but should not be mistaken for hot-spring bathing, tourism, or facility adoption. The DOE figures include power generation, heat pumps, district heating, and other direct uses.
| Measure | Figure | Period and scope |
|---|---|---|
| U.S. installed geothermal power capacity | 3.673 GW | 2020, all geothermal power |
| U.S. share of world online geothermal capacity | Close to 25% | 2020 estimate |
| California and Nevada share of U.S. geothermal power capacity | More than 90% | 2020 estimate |
| U.S. geothermal direct-use capacity | 485 MWth | 2020 report |
| U.S. geothermal heat-pump installations | More than 1.7 million units | 2020 report |
| Residential share of heat-pump installations | About 40% | 2020 estimate |
Geothermal contributed less than 1% of U.S. energy capacity in 2020. DOE also estimated more than 320 GWth of U.S. geothermal direct-use economic resource potential in its 2021 resource-maximization page, while only about 100 MWth had been deployed for district heating across 21 U.S. installations in the underlying 2017 analysis.
The forward-looking figures are scenarios, not observed hot-spring demand: DOE estimated 231 GW of direct-use potential by 2050 and projected 60 GW of always-on geothermal baseload capacity by 2050. Both include uses broader than bathing.
Sources: Now Available: IEA 2020 U.S. Geothermal Report and Resource Maximization (DOE).
Hot Spring Hydrotherapy Pain and Function Statistics
Clinical evidence in the supplied research concerns selected people with chronic low back pain, not healthy visitors or every type of hot spring. The systematic review and meta-analysis reported standardized mean differences, so the results summarize relative outcomes across heterogeneous interventions and scales.
| Outcome | Pooled result | Statistical context |
|---|---|---|
| Pain intensity | SMD −0.901 | 95% CI −1.777 to −0.025 |
| Functional disability | SMD −3.236 | 95% CI −4.898 to −1.575; I²=98.4% |
| Quality of life | SMD 0.104 | 95% CI −0.397 to 0.606; P=0.683; I²=86.30% |
| Drug dosage | SMD −0.471 | 95% CI −0.922 to −0.020; P=0.041; I²=70.70% |
The pain and drug-dosage pooled estimates were statistically distinguishable from no effect under the reported analyses, but heterogeneity was substantial. The very high dysfunction heterogeneity and high quality-of-life heterogeneity limit how confidently one pooled result can be transported to a different spring, protocol, or patient group.
Source: The Impact of Hot Spring Hydrotherapy on Pain Perception and Dysfunction Severity in Patients with Chronic Low Back Pain: A Systematic Review and Meta-Analysis (peer-reviewed review).
Hot Spring Treatment, Quality-of-Life, and Safety Evidence
The review found a stronger response among participants aged 60 and older than among younger subgroups for pain-related outcomes. For participants younger than 60, the reported pain subgroup effect was SMD −0.561 with P=0.885; the subgroup was not statistically significant and may reflect limited evidence.
Publication-bias tests were also reported, but their power is limited in small evidence bases. The pain test gave an Egger slope coefficient of −1.01174 with P=0.488, while the quality-of-life test gave −2.607475 with P=0.231.
One controlled Hungarian trial used 42°C thermal-mineral water on 15 occasions over 3 weeks for adults with chronic low back pain. Movement-pain VAS, measured on a 0–100 mm scale, changed as follows:
- In the balneotherapy group, the mean was 66.82 at baseline, 26.69 at week 3, and 20.09 at week 12.
- In the control group, the mean was 63.67 at baseline, 67.35 at week 3, and 70.23 at week 12.
- The trial assessed outcomes at baseline, week 3, and week 12, with between-group differences reported at both follow-ups at P<0.001.
These are within-trial measurements from one protocol, not population estimates. Water chemistry, temperature, session frequency, comparison treatment, and participant characteristics limit direct generalization to other hot springs or home bathing routines.
Source: The effects of immersion in 42℃ radon, natrium, calcium, bicarbonate content thermal-mineral water on chronic low back pain (peer-reviewed trial).