Primary data (the numbers)
These sources feed the visit counts, crowd timing, weather, and access scoring you see on every park page. All four are U.S. federal government works in the public domain under 17 U.S.C. § 105. How we turn them into scores is described on the methodology page.
NPS Visitor Use Statistics
Monthly recreation-visit counts for every reporting NPS unit, going back to 1979. This is the basis for every visitation figure, busiest/quietest-month label, five-year average, trend chart, and crowd ranking on the site.
NOAA NCEI U.S. Climate Normals (1991–2020)
Thirty-year monthly averages of high/low temperature, precipitation, and snowfall for a weather station near each park. These drive the weather columns and the comfort score on each park's calendar.
NPS Data API — unit metadata & photography
Official unit names, designations, states, coordinates, the link to each park's NPS page, and the public-domain hero photography we display. Used to make sure every unit is named and classified exactly as the Park Service does.
NPS seasonal road & conditions pages
Typical seasonal open/close windows for each park's main roads, read from the park's own NPS "plan your visit" road and conditions pages. These feed the month-by-month access score. Because real dates move with the snow each year, we treat them as typical and link to the live page for current status.
Sources we cite
The writing also points you to authoritative pages for anything specific, time-sensitive, or worth confirming before you act on it — fees, reservations, lodging windows, safety guidance, conditions. We link to these; we do not ingest data from them.
- NPS park pages — wildlife, safety, fees, and current-conditions pages for each unit, for operating facts and wildlife-behavior windows.
- Recreation.gov — federal timed-entry, permit lottery, and campground reservations.
- NPS-authorized concessioners — the operators who publish official lodging windows and rates (for example Yellowstone National Park Lodges, Yosemite Hospitality, Grand Canyon National Park Lodges). We link to the operator so you book and confirm at the source.
- AirNow (EPA and partners) — air-quality and wildfire-smoke awareness during fire season.
- U.S. Naval Observatory — sunrise and sunset times used in the photography-timing notes. These values are looked up at the time of writing and stored with the page; they are not pulled live.
- USGS Store — where the federal "America the Beautiful" interagency pass is sold, linked from accessibility and fee notes.
- NPS cooperating associations — park partners such as Yellowstone Forever, Yosemite Conservancy, and Grand Canyon Conservancy, whose visitor-education materials inform some editorial context.
Photography & image policy
Park photography on this site comes from the NPS Data API and is NPS-created public-domain imagery under 17 U.S.C. § 105. Each image carries the credit line the Park Service supplies (for example NPS / Jim Peaco). Any image whose credit is blank, non-NPS, or carries a usage notice is held for manual review before it can appear — we don't publish an image we can't confirm is free to use.
Federal data is public domain. Our analysis is ours.
The underlying datasets are U.S. government works, free of copyright. The scoring, rankings, editorial, and design on this site are our own work. National Sites Guide is independent — not affiliated with or endorsed by the National Park Service, and we don't use the NPS Arrowhead or other NPS marks. If a source link breaks or a figure looks wrong, tell us via the contact form.