Fort Mason is one of the most photographed neighbourhoods in America, and the maps still can't find our front doors. For almost a decade, packages here have gone to the wrong house. The challenge: fix the addresses in the major map systems, for real, scored by a machine.
Type a Fort Mason address the way it's written on your mail. We'll show your real front door, and where the maps send the delivery driver instead.
🟢 the real front door · 🔴 where a map sends the driver · 🟣 the City's other address with the same name
Order something to a home inside Fort Mason and there's a good chance it lands at the wrong door. Packages for one house are routinely left at another house 250 m away. Drivers give up, leave the box on a stranger's porch and photograph it. Google mostly copes; Apple Maps, many delivery apps and the US government's own geocoder don't.
Why: Fort Mason has two address systems for the same buildings.
Lose the ZIP code and you're downtown. Search for "3 Fort Mason" and the government geocoder finds nothing at all.
| Building | What we use | What the City uses |
|---|---|---|
| Haskell House | 3 Fort Mason | 3 Franklin St (twin at Market St) |
| Quarters 2 | 2 Fort Mason | 2 Franklin St (twin at Market St) |
| Quarters 4 | 4 Fort Mason | 4 Franklin St (twin at Market St) |
| Building 9 | 9 Fort Mason | 9 MacArthur Ave |
| Residences 36–39 | 36–39 Fort Mason | 36–39 MacArthur Ave |
| 41–49 | 41–49 Fort Mason | no official address point |
Sources: City and County of SF Enterprise Addressing System; OpenStreetMap; US Census geocoder. Re-run it yourself: scripts/crosscheck.py.
For each Fort Mason address, we ask each map system "where is this?". The answer passes if it lands within 60 m of the right building. A system is fixed when its card is fully green and stays green for 30 days. Last run: 2026-10-06.
Every address, every system (24 addresses).
| Address | US Census | OSM Nominatim | Photon (OSM) |
|---|---|---|---|
| 2 Fort Mason Quarters 2 | ✗ (not found) | ✗ (288 m off) | ✓ (4 m) |
| 3 Fort Mason Haskell House | ✗ (not found) | ✗ (338 m off) | ✓ (1 m) |
| 4 Fort Mason Quarters 4N and 4S | ✗ (not found) | ✗ (368 m off) | ✓ (3 m) |
| 9 Fort Mason Building 9 | ✗ (not found) | ✗ (233 m off) | ✗ (217 m off) |
| 32 Fort Mason Building 32 | ✗ (not found) | ✓ (1 m) | ✓ (1 m) |
| 33 Fort Mason Building 33 | ✗ (not found) | ✓ (1 m) | ✓ (1 m) |
| 34 Fort Mason Building 34 | ✗ (not found) | ✓ (2 m) | ✓ (2 m) |
| 35 Fort Mason Building 35 | ✗ (not found) | ✓ (2 m) | ✓ (2 m) |
| 36 Fort Mason Building 36 | ✗ (not found) | ✓ (1 m) | ✓ (1 m) |
| 37 Fort Mason Building 37 | ✗ (not found) | ✓ (2 m) | ✓ (2 m) |
| 38 Fort Mason Building 38 | ✗ (not found) | ✓ (2 m) | ✓ (2 m) |
| 39 Fort Mason Building 39 | ✗ (not found) | ✓ (1 m) | ✓ (1 m) |
| 41 Fort Mason | ✗ (not found) | ✓ (1 m) | ✓ (1 m) |
| 42 Fort Mason | ✗ (not found) | ✗ (64 m off) | ✓ (1 m) |
| 43 Fort Mason | ✗ (not found) | ✓ (48 m) | ✓ (1 m) |
| 44 Fort Mason | ✗ (not found) | ✓ (23 m) | ✓ (1 m) |
| 46 Fort Mason | ✗ (not found) | ✗ (95 m off) | ✓ (1 m) |
| 47 Fort Mason | ✗ (not found) | ✓ (2 m) | ✓ (2 m) |
| 48 Fort Mason | ✗ (not found) | ✓ (2 m) | ✓ (2 m) |
| 49 Fort Mason | ✗ (not found) | ✓ (1 m) | ✓ (1 m) |
| 101 Fort Mason Golden Gate National Recreation Area - Cultural Resources | ✗ (not found) | ✓ (0 m) | ✓ (0 m) |
| 102 Fort Mason San Francisco Conservation Corps | ✗ (not found) | ✓ (8 m) | ✓ (0 m) |
| 102 Fort Mason Building 102 | ✗ (not found) | ✓ (1 m) | ✓ (9 m) |
| 201 Fort Mason William H. Whelan Building | ✗ (not found) | ✗ (191 m off) | ✓ (1 m) |
People, AI agents, or people with agents. Every claim needs evidence someone else can re-run.
Former military and federal sites around San Francisco show the same disease. Our detector compares the addresses people use (OpenStreetMap) with the City's official points. These are candidates, to be confirmed on the ground. In the Presidio, for example, "100 Montgomery St" exists both there and in the Financial District, 5.2 km apart.
| Area | Addresses checked | Match | Two systems | No official point |
|---|---|---|---|---|
| Fort Mason | 81 | 47 | 16 | 18 |
| Presidio of San Francisco | 701 | 671 | 19 | 11 |
| Treasure Island + Yerba Buena Island | 307 | 235 | 14 | 58 |
| Hunters Point Shipyard | 196 | 191 | 3 | 2 |
Know another stranded neighbourhood? Add it to data/areas.json and open a pull request.
Your stories are the evidence. Send the organiser, on the Fort Mason neighbours chat:
Nothing is published without your OK, and never with your name.