{"nrhp_refnum":"89000358","name":"Mercersburg Historic District (Boundary Increase)","other_names":["See Also:Mercersburg Historic District"],"category":"district","location":{"address":"S. Main St., between Linden Ave. and PA 75","address_restricted":false,"city":"Mercersburg","county":"Franklin County","state":"PA","lat":39.82317423650005,"lon":-77.90220899876607,"geom_source":"nps_gis"},"listed_date":"1989-05-17","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Architecture"],"significance_levels":["local"],"summary":{"what_it_is":"A boundary increase to the Mercersburg Historic District, adding twelve mostly residential properties along South Main Street between Linden Avenue and Constitution Street in Mercersburg, Franklin County, Pennsylvania. The buildings date from the late 18th through early 20th centuries.","why_significant":"The area is significant for its architecture, showing vernacular buildings from the 18th and 19th centuries alongside Colonial Revival houses from about 1910. The two large Colonial Revival mansions, Prospect and Rosemont, mark the town entrance and reflect the conversion of a former brick yard site to a landscaped residential estate tied to the Byron tannery. The area also connects to the town's industrial and commercial history.","narrative":"Along South Main Street, where the road bends east at Linden Avenue, twelve properties form a boundary increase to the Mercersburg Historic District. The most prominent is Prospect, a two-and-one-half-story brick Colonial Revival mansion built in 1910 for Harry W. Byron, son of the founder of the Byron Tannery, which was the town's principal industry in the late 19th and early 20th centuries. Its slate gambrel roof, pedimented portico and marble and mahogany interiors set it apart in the area. Rosemont, a nearby Colonial Revival house from about 1910, stands on a triangular lot. Across the street, a row of log, brick and frame houses dating from the late 18th through early 20th centuries recalls the period when the site was a brick yard beside a foundry at the edge of town. The houses are regarded as consistent in age, materials and integrity with the existing district.","period_of_significance":"1780-1920","architect_builder":null,"architectural_style":"Colonial Revival; Cumberland Valley Vernacular","criteria":["C"],"status_note":"Prospect was historically rehabilitated in 1987 and has operated as an inn intermittently since the 1950s; 213 S. Main Street has been an antique shop in recent years.","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:37.508648-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/89000358.pdf"},"photo":null,"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71996488","wikipedia":null,"wikidata":null},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/franklin-county/mercersburg-historic-district-boundary-increase-89000358/"}