Keystone Atlas

A Layered Map of Pennsylvania — markers shown

Drawing the Commonwealth…

Keystone Atlas

A layered map of Pennsylvania

Every Pennsylvania historical marker with a known location — 2,585 of them, merged from the PHMC's export and its live map service — plus seventy layers of parks, trails, waterways, boundaries, geology, mine workings, natural landmarks and vanished places, drawn over real street geography.

How to use it

Search everything — markers, every loaded layer and the USGS gazetteer at once.
Map style heads the layer list: pick one of four sheets to draw on — roads, terrain, plain paper or satellite — and stack the topo quads and railways over it.
Layers load the first time you tick them; large ones fetch only what the viewport covers.
Filter markers by county, type, and dedication decade.
Measure draws a running distance along as many points as you click.
Copy link captures the view, base map, active layers and decade in a shareable URL.

Data sources & credits

Live layers come from PASDA (Pennsylvania Spatial Data Access, Penn State), whose underlying agencies include the PHMC, DCNR and the PA Geological Survey, PennDOT, DEP, the Fish & Boat and Game Commissions, WeConservePA, FEMA, NGS, the USGS and HIFLD. County geometry is U.S. Census via us-atlas. Street tiles © OpenStreetMap contributors; hillshade and satellite imagery by Esri; USGS topographic quads via Esri; railway overlay © OpenRailwayMap contributors (CC-BY-SA). Marker text and details are from the Pennsylvania Historical & Museum Commission.

Honesty about the data

County high points are the highest named summit per county; the true maximum is a separate layer, and rarely the same place.
Digitized mined areas were traced from operators' own mine maps — what was reported worked out, not a verified void.
DEP's dam status and type letters have no published key, so they are shown as-is rather than guessed at.
Covered bridges and fire towers are filtered from the GNIS gazetteer by name — named features, not a complete inventory.
"Places that are gone" are features GNIS marks (historical); no closure date or cause is recorded.
Trail activity flags are undocumented codes read as permitted/not; unknowns are omitted.
A fetch that hits the paging cap says so rather than reporting a truncated count.

Keep the Atlas free

No sign-in wall, and no layer held back for a paid tier. The hosting and map-tile bills are real, monthly, and mine.

If this map has told you something about Pennsylvania you didn't already know, chipping in is what keeps it that way.

Chip in on Ko-fi

Any amount helps. So does telling someone about it.

Privacy

No analytics, no ads, no account, no cookies. The only thing kept is a flag on your device remembering you've seen this box — clear your browser data and it's gone.

I don't collect anything about you. I genuinely can't tell you how many people use this map, because I don't measure it.

Legal

This is an independent, personal project — not affiliated with, endorsed by, or representing the Commonwealth of Pennsylvania, the PHMC, or any other agency. All data is drawn from public sources and presented as-is, with no warranty of accuracy or completeness. Do not rely on it for navigation, property or legal-boundary determinations, or safety decisions — the flood-hazard, abandoned-mine and underground-workings layers in particular are informational only. Nothing here establishes whether a given piece of ground is undermined; consult DEP and the official sources.