I would say the Telegraph. In the book [CODE: The Hidden Language of Computer Hardware and Softwar](https://www.amazon.com/Code-Language-Computer-Hardware-Soft

I would say the Telegraph. In the book [CODE: The Hidden Language of Computer Hardware and Softwar](https://www.amazon.com/Code-Language-Computer-Hardware-Software/dp/0735611319 https://www.amazon.com/Code-Language-Computer-Hardware-Softw...), Charles Petzold talks about how it's foundational to the eventual invention of the computer. Back then, it also meant coast to coast communications were almost instantaneous. And soon after, transatlantic cable-enabled telegraph boosted commerce between America and Europe.