Kathy Loves Physics & History did a video on this, and the reason is basically legacy: * https://www.youtube.com/watch?v=7yRGvMgieEU https://www.youtube.com/wa

Kathy Loves Physics & History did a video on this, and the reason is basically legacy: * https://www.youtube.com/watch?v=7yRGvMgieEU https://www.youtube.com/watch?v=7yRGvMgieEU Edison originally purchased others' dynamos, especially Wallace-Farmer, which was 110V (DC): * https://americanhistory.si.edu/collections/search/object/nmah_705221 https://americanhistory.si.edu/collections/search/object/nma... * https://en.wikipedia.org/wiki/Moses_G._Farmer https://en.wikipedia.org/wiki/Moses_G._Farmer So Edison's long-legged Mary-Ann was also 110V: * https://www.collectorsweekly.com/stories/82967-thomas-edison-dynamo-long-legged-mary-a https://www.collectorsweekly.com/stories/82967-thomas-edison... * https://edison.rutgers.edu/life-of-edison/inventions?view=article&id=530:electric-generator&catid=91 https://edison.rutgers.edu/life-of-edison/inventions?view=ar... * https://americanhistory.si.edu/collections/search/object/nmah_1287625 https://americanhistory.si.edu/collections/search/object/nma... Light bulbs in the early 1900s were first designed for lower voltages, and the grid slowly raised things over time, but at some point they couldn't go any higher because it would start blowing things, so they were 'stuck' in the 110-120V range.