{"nrhp_refnum":"80000665","name":"Great Blue Hill Weather Observatory","other_names":["Blue Hill Meteorological Observatory"],"category":"building","location":{"address":"Milton","address_restricted":false,"city":"Milton","county":"Norfolk County","state":"MA","lat":42.21199383700008,"lon":-71.11425701874904,"geom_source":"nps_gis"},"listed_date":"1980-09-25","is_nhl":true,"nhl_designated_date":"1989-12-20","areas_of_significance":["Science","Architecture","Invention"],"significance_levels":["national","state"],"summary":{"what_it_is":"A weather observatory building with a crenellated tower and simple stone sheds on top of Great Blue Hill in Milton, Massachusetts, dated to 1885 and possibly designed by A. Lawrence Rotch.","why_significant":"The nomination calls it the most important historic building in the Blue Hills area and the foremost landmark in the history of American weather forecasting. It was the site of the earliest experiments using balloons and kites to lift weather instruments. Harvard later administered research there, producing pioneering work on cloud classification and fog.","narrative":"Great Blue Hill Weather Observatory occupies the summit of Great Blue Hill in Milton, Massachusetts, at 635 feet, the highest elevation within ten miles of the Atlantic along the East coast. Built in 1885 of granite rubble, it has a crenellated tower and simple stone sheds. Concrete additions were made over the stone around 1916, and federal weather agency staff later added a library and further space. A. Lawrence Rotch is named as the possible architect and original owner. The observatory is described as the foremost landmark in the history of American weather forecasting. Researchers here carried out the earliest experiments using balloons and kites to lift recording instruments, and readings of wind velocity, temperature and humidity at different heights became standard tools for prediction. Within ten years its forecasts were notably accurate. Harvard took over the research in the early twentieth century and published pioneering studies of cloud classification and fog. The site still records weather and is an International Climatological Benchmark Station.","period_of_significance":null,"architect_builder":"Possibly A. Lawrence Rotch","architectural_style":"Crenellated tower, simple stone sheds","criteria":[],"status_note":"Used for meteorological recording; later additions include a library and space added by the National Oceanographic and Atmospheric Administration. Designated an International Climatological Benchmark Station.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:11:55.073688-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/97/7923/63792397/content/electronic-records/rg-079/NPS_MA/80000665.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/80000665/78d8b0dadc-800.webp","url_1600":"https://nationalhistoricalregister.com/media/80000665/78d8b0dadc-1600.webp","licence":"CC BY-SA 3.0","author":"Jameslwoodward","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Great_Blue_Hill_Weather_Station_Milton_MA_03.jpg\" rel=\"noopener\">Jameslwoodward</a>, <a href=\"https://creativecommons.org/licenses/by-sa/3.0\" rel=\"license noopener\">CC BY-SA 3.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Great_Blue_Hill_Weather_Station_Milton_MA_03.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/63792397","wikipedia":"https://en.wikipedia.org/wiki/Blue_Hill_Meteorological_Observatory","wikidata":"https://www.wikidata.org/wiki/Q1803017"},"indexable":true,"url":"https://nationalhistoricalregister.com/massachusetts/norfolk-county/great-blue-hill-weather-observatory-80000665/"}