Trailmark: the national parks map you fill in as you travel

01  What Trailmark is

Trailmark is a national parks passport that lives in a browser tab. It places all 63 designated U.S. National Parks on one hand-drawn topographic map and asks a single question about each: have you stood in it? Tap the parks you have, and each one stitches an enamel patch onto the map in its own place, turns a progress ring another notch and nudges a percentile line that ranks your collection against other visitors.

It is free and ad-supported, with no account, no email, nothing to install and no paid tier. That matters more here than it usually does: a parks list you began years ago is worthless if it needs a login you have forgotten.

It is also not a trip log. There are no dates, notes, photographs or check-ins — the collection is a set of names. That is why filling in twenty years of travel from memory takes about a minute, and why you will keep adding after each trip rather than back-filling a diary.

02  How the map works, and why it needs a list underneath

The map is a drawing, not a tile layer: one hand-made SVG survey of the United States with contour lines and a survey-sheet look. It holds four surfaces — the contiguous 48 states carry 51 of the parks, and Alaska, Hawaiʻi and the island territories get a labelled inset frame each for their eight, two and two — and all 63 fit on a phone screen at once, with no scrolling.

The parks sit at their real coordinates, which creates a problem the app solves rather than hides. Kings Canyon and Sequoia are a few miles apart in the Sierra Nevada — a few units apart on a 960-unit canvas — and no pair of tappable markers can honestly be separated at that distance. So a tap resolves to whichever park is genuinely nearest, deterministically. The precise, keyboard-operable path is the search list below the map: type a park name or a state code and toggle it there.

Each park wears an original enamel medallion, filled from one of six biomes — alpine, meadow, canyon, basin, basalt, coastal — and drawn with one of twelve generic marks: a peak, an arch, a geyser, a saguaro. Your newest addition carries a trail-blaze pin, and at sixty-three a ribbon across the map reads ALL 63 BAGGED. None of it is NPS artwork; the patches, glyphs and contours are the app's own drawings.

03  The percentile is an estimate, and the app says so

Add a park or two and a line appears under the progress ring: "Top 34% — you've out-travelled 66% of visitors."

The baseline is a modelled curve of how many parks visitors have actually seen, anchored at a handful of points and interpolated between them on a log scale because the tail thins out fast. The app's own anchors: one park is top 82%, three top 54%, five top 34%, twelve top 11%, twenty-five top 2.6%, thirty-five top 1%, and all sixty-three top 0.05%.

Two things follow. The early parks move the number enormously and the late ones hardly at all — one park to five is worth more of this figure than twenty-five to thirty-five, though the second is far harder. The curve is deliberately cautious rather than flattering, presented in the footer of every page as an estimate, not a record.

There is an upgrade path too. The figure comes from that model until fifty collections have been recorded through the app's shared tally, after which it reads the live sizes of real collections; below fifty the sample is not representative, since the first visitor would otherwise be told they were in the top 100%. If the tally is unreachable, the model stays rather than blocking your map behind a network call.

04  Your whole collection fits in one link

This is the part worth understanding on day one, because it is how the app manages without accounts. Your collection is saved twice: on the device, in your browser's own storage, restored silently the next time you open the page; and in the address bar, as a growing-link. That link is the only bridge between your phone and your laptop.

The link is not a save file on a server. It is the collection itself — a 63-bit mask, one bit per park in a frozen alphabetical order that will not be reshuffled, written in base64url with trailing empty bytes trimmed so a small collection produces a short link. The address bar updates as you tap, without filling your browser history. Copy the URL into a note and you have a backup that survives a cleared cache, a new phone and a borrowed laptop.

Press Make my patch-map and you get a framed card — lit map, count out of 63, patches earned, percentile — with actions beneath it. Share hands it to your phone's share sheet; on a desktop, where there is no share sheet, it copies the brag line and the link together, because a bare URL pasted into a group chat is a wasted impression. Download PNG saves it as trailmark-21-of-63.png.

The card is not a screenshot: it is the same renderer the server rasterises to a 1200 by 630 image, so what you see is what a chat app fetches when your link is pasted. That is also why its percentile comes from your count rather than the live tally — an image that changed between the preview and the download would not be the same artifact.

05  Trail series: fifteen smaller runs inside the 63

Sixty-three is a long climb, so the app breaks it up. A panel under the progress ring lists fifteen named trail series, each a small set of parks sharing something real. Some are a whole state — the California Nine, the Alaska Eight, the Utah Five, the Colorado Four, the Florida Three. Others cut across the map: No Road In gathers the five parks reachable only by boat or plane, The Underground Three the parks named for the cave beneath them, The Volcano Line six built by fire, The Four Deserts the eight in the Chihuahuan, Sonoran, Mojave or Great Basin desert. The First Fifteen collects those designated before 1920; This Century the eight designated since 2000.

The panel is ordered the way a collector reads it, not alphabetically: sets you have started first, closest to finishing at the top; completed sets next, biggest first; untouched sets last, smallest first. Within three parks of closing a set it stops counting and names them — "To go: Zion." — and finishing one stamps the card complete.

The series are the app's own grouping, not an official one, and the state and year sets are derived from the park data itself so they cannot drift out of step with the map. Their real job is trip planning: "thirty-seven of sixty-three" tells you nothing about where to go next, while "one park from finishing the Utah Five" is an itinerary.

06  Questions people ask

How many national parks are there in the United States?

Sixty-three carry the National Park designation, which is what Trailmark tracks — from Yellowstone, established in 1872, to the newest additions of the 2010s. The National Park Service manages hundreds of other units as well, including national monuments, seashores and historic sites, and those are not part of the 63 on this map. Trailmark is not affiliated with the National Park Service.

Is Trailmark free, and do I need an account?

It is free and ad-supported, with no account, no email and no password. There is no paid tier and nothing is locked behind a purchase. The app runs in your browser and keeps your collection on your own device, so no part of your map requires a login.

Will I lose my map if I clear my browser or change phones?

Clearing your browsing data on a device does clear the save stored on that device, and a device save does not travel to a new phone on its own. The growing-link is the fix: copy it out of the address bar, save it somewhere, open it on any other device and your exact collection comes back. Treat the link as the real copy and the device save as the convenience.

Can I add national parks I visited years ago?

Yes, and that is the intended way to start. There are no dates or check-ins to enter — you tap the parks you remember having stood in, in whatever order they come back to you, and the map fills in. A park you saw as a child counts exactly the same as one you saw last month.

Is the "top X%" ranking real?

It is an honest estimate rather than an official record, and the app labels it that way. Up to a point it comes from a deliberately cautious model of how many parks visitors have seen; once enough collections have been recorded it switches to a live read of real collections. Either way it is a rough sense of where you stand, not a certificate.

Does Trailmark work on a phone, or offline?

It is built for a phone first, and the whole map — all 63 parks including the Alaska, Hawaiʻi and territory insets — fits on screen without pinching. The page needs to load once over the network; after that your collection lives in the browser, and the ranking call fails quietly, so losing signal never costs you a tap.

07  More from the shelf

• Lexicon — Tap the words you know. Get your number.
• Focus Fern — Grow a garden while you focus.
• Countmark — Count down to every big day.
• Isobath — Drop a pin. Find out how wrong you were.

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