Where this comes from
The tile index and the archive tiles are the DRCOG Regional Data Catalog , licensed CC BY 3.0 . 2018 to 2024 stream from DRCOG's mosaics hosted by Sanborn Geospatial; 2004 to 2016 are read straight from the raw GeoTIFFs on DRCOG's S3 archive, a few hundred bytes at a time, one image row per request, so nobody has to download a 446 MB file. 2002 (JPEG 2000) and 2008 (MrSID) are offered as downloads, except inside Arapahoe County, where the county's own service fills them in. The base map under the square is your pick of Bing, Esri world imagery, OpenStreetMap, or a whole DRAPP year — 2018 to 2024 render region-wide from the same mosaics, and Esri’s World Imagery Wayback has one Esri basemap per year back to 2014. Addresses are placed by the U.S. Census Bureau geocoder, falling back to Nominatim .
Before DRAPP there is no regional programme, so the older years come from whoever flew them and cover only their own ground: Arapahoe County (2026, 2000, and a black-and-white 1998), Boulder County (2000 and a 1 ft black-and-white 1977), South Metro Fire Rescue's decade-by-decade scans of its district from the 1950s to the 1990s, CDOT's scans of Golden in 1930, Boulder in 1948 and Englewood–Littleton in 1953, and the Denver Public Library 's georeferenced 1933 King aerial survey of central Denver. Outside their footprints those years simply say so.
Every year is rendered on the same ground square (Colorado State Plane Central) and then warped onto the map, so features line up year to year — the county services draw onto that grid themselves, and the library's Web Mercator tiles are mosaicked and warped onto it here. Use ← and → to step through loaded years. Source and notes on GitHub . Part of myjimmycloud.com .
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