{"nrhp_refnum":"89002288","name":"Hopkinton Dam and Spillway","other_names":[],"category":"structure","location":{"address":"E end of Hopkinton Reservoir in Hopkinton State Park","address_restricted":false,"city":"Ashland","county":"Middlesex County","state":"MA","lat":42.25644476600007,"lon":-71.51086590271296,"geom_source":"nps_gis"},"listed_date":"1990-01-18","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Community Planning and Development","Engineering","Politics/Government"],"significance_levels":["state","local"],"summary":{"what_it_is":"A dam and granite spillway in Hopkinton State Park in the southwest corner of Ashland, Middlesex County, Massachusetts, built in 1891-94 across Indian Brook as part of a metropolitan water supply system.","why_significant":"The dam and spillway are tied to the Sudbury River water supply, the second source tapped by the Metropolitan Water Board. They are good examples of late 19th century water technology and design. The granite spillway is called particularly outstanding for its sculptural, stream-like appearance.","narrative":"Built between 1891 and 1894 across Indian Brook, this dam and spillway sit in Hopkinton State Park in the southwest corner of Ashland. The dam is an earthen embankment with a concrete core wall resting on bedrock, plastered with Portland cement on the upstream side and faced with granite blocks. At its west end, a 30-foot overfall leads into a 650-foot spillway that descends through a series of granite-paved steps with rounded granite coping, giving the look of a brook running through the woods. The structure was one of the later additions to the Sudbury River supply and storage system, which began in the 1870s and also includes the Framingham Reservoirs and the Sudbury Aqueduct. Two gate chambers once fed an overflow channel and filter beds, which have since been removed and replaced by a sandy beach. The dam and spillway are valued for their link to Boston's metropolitan water supply and for their late nineteenth century engineering and design.","period_of_significance":null,"architect_builder":null,"architectural_style":null,"criteria":["A","C"],"status_note":"Condition is described as good. The dam and spillway were removed from water-supply service when the reservoir was turned over to the Commonwealth for use as a state park.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:12:59.736899-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/6/7920/63792006/content/electronic-records/rg-079/NPS_MA/89002288.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/89002288/b67f9a1f0c-800.webp","url_1600":"https://nationalhistoricalregister.com/media/89002288/b67f9a1f0c-1600.webp","licence":"CC BY 3.0","author":"John Phelan","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Hopkinton_Dam_and_Spillway,_Ashland_MA.jpg\" rel=\"noopener\">John Phelan</a>, <a href=\"https://creativecommons.org/licenses/by/3.0\" rel=\"license noopener\">CC BY 3.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Hopkinton_Dam_and_Spillway,_Ashland_MA.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/63792006","wikipedia":"https://en.wikipedia.org/wiki/Hopkinton_Dam_and_Spillway","wikidata":"https://www.wikidata.org/wiki/Q5900778"},"indexable":true,"url":"https://nationalhistoricalregister.com/massachusetts/middlesex-county/hopkinton-dam-and-spillway-89002288/"}