The London Underground was not built by a single entity but by a series of competing private companies in the mid-19th and early 20th centuries. The very first line, the Metropolitan Railway, was championed by Charles Pearson and opened in 1863 using a "cut-and-cover" method (digging up a road and roofing it over). Later, the "Tube" (the deep-level lines) was made possible by engineers like James Henry Greathead, who developed the tunneling shield. In the early 1900s, American financier Charles Tyson Yerkes played a massive role in consolidating several lines and electrifying the system through his company, the Underground Electric Railways Company of London (UERL). It wasn't until 1933 that these disparate private lines were unified under public ownership as the London Passenger Transport Board. So, while Pearson provided the vision, it was a mix of Victorian engineers and Edwardian capitalists who actually constructed the physical network.