Data were provided by the USA National Phenology Network.

USA National Phenology Network. Historical Annual Spring Indices (NCEP), First Leaf and First Bloom, 2016–2024, contiguous United States. USA-NPN, Tucson, Arizona, USA. Accessed September 17, 2026. https://www.usanpn.org/data/maps/spring ; https://doi.org/10.5066/F7SN0723 . First Bloom 2017 was absent from the service catalog and is omitted.

USA National Phenology Network. 2019. Land Surface Phenology 2001–2017 for the United States. Mid Greendown Median and Mid Greendown Median Absolute Deviation. USA-NPN, Tucson, Arizona, USA. Accessed September 17, 2026. https://www.usanpn.org/data/maps/land_surface_phenology . These summarize satellite vegetation change, not peak foliage color or individual annual observations.

License: Creative Commons Attribution 4.0 International. https://creativecommons.org/licenses/by/4.0/ . Provider policy: https://www.usanpn.org/about/terms . No endorsement implied.

Changes: rasters requested via WCS with nearest-neighbor sampling, EPSG:4326 bounds [-125,24,-66,50], 708 columns by 312 rows. The application samples cells on device. Spring ranges are computed from available annual modeled dates. Autumn context uses published median ± MAD; it is not a prediction confidence interval. Exact request URLs, provider time slices, retrieval date, byte lengths, and SHA-256 hashes are recorded in earth-history-manifest.json. The fetch script is tools/fetch_earth_history.py.