{"nrhp_refnum":"80001370","name":"Keystone Building","other_names":[],"category":"building","location":{"address":"30 S. Stolp Ave.","address_restricted":false,"city":"Aurora","county":"Kane County","state":"IL","lat":41.75738892700008,"lon":-88.31576872299996,"geom_source":"nps_gis"},"listed_date":"1980-03-18","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Architecture"],"significance_levels":["national"],"summary":{"what_it_is":"A four-story brick and terra cotta office building at 30 South Stolp Avenue on Stolp Island in downtown Aurora, Kane County, Illinois, built 1922-23 to designs by George Grant Elmslie with L. A. Fournier as associate architect.","why_significant":"The nomination argues it is the largest private office building designed by George Grant Elmslie and probably the largest Prairie School office building of its type. It was Elmslie's first commission after his split from William G. Purcell and reflects the philosophy of his mentor Louis Sullivan. It is also noted for its skillful incorporation of part of an earlier building on an awkward site.","narrative":"Rising four stories on Stolp Island in downtown Aurora, this office building was completed in 1922-23 from designs by George Grant Elmslie, with L. A. Fournier as associate architect. Its facade is brown glazed brick flecked with iron, accented by terra cotta belt courses, large shields and a decorative cornice glazed in brown, green and blue. Shops with private entries line the ground floor, and small office suites fill the upper levels around a central lobby, an original skylight and oak trim. Part of an earlier Aurora Silverplate Company building was incorporated into the northeast portion, a feat the nomination calls a triumph of planning on an irregular lot. It was Elmslie's first commission after leaving his partnership with William G. Purcell. The nomination describes it as the largest private office building he designed and probably the largest Prairie School building of its type, echoing the base, shaft and crown composition favored by Louis Sullivan. It remained largely unaltered and in excellent condition.","period_of_significance":"1900- (specific dates 1922-23)","architect_builder":"George Grant Elmslie, Architect; L. A. Fournier, Associate Architect","architectural_style":"Prairie School office building","criteria":[],"status_note":"Described as in excellent condition, unaltered and occupied, with a superb facade; the only intrusions noted are window air conditioning units and some interior upgrades.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:55:35.850608-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/28/8931/28893128/content/electronic-records/rg-079/NPS_IL/80001370.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/80001370/4e5ad970b4-800.webp","url_1600":"https://nationalhistoricalregister.com/media/80001370/4e5ad970b4-1600.webp","licence":"CC0","author":"Smallbones","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Keystone_Aurora_IL.jpg\" rel=\"noopener\">Smallbones</a>, <a href=\"http://creativecommons.org/publicdomain/zero/1.0/deed.en\" rel=\"license noopener\">CC0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Keystone_Aurora_IL.jpg"},"district":{"nrhp_refnum":"86001487","name":"Stolp Island Historic District","url":"https://nationalhistoricalregister.com/districts/illinois/stolp-island-historic-district-86001487/"},"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/28893128","wikipedia":"https://en.wikipedia.org/wiki/Keystone_Building_(Aurora,_Illinois)","wikidata":"https://www.wikidata.org/wiki/Q6398451"},"indexable":true,"url":"https://nationalhistoricalregister.com/illinois/kane-county/keystone-building-80001370/"}