The first generation of modern computing history is said to have begun around the late 1930s. Zuse in Germany and Atanasoff in the USA developed basic computers. The work of neither was recognised widely.
Similarly, the world's first digital computer, Colossus, was developed out of the public eye at Bletchley Park. The British built it in secret during World War 2, with the help of Alan Turing, to decode messages from the German ENIGMA machine.
ENIAC, however, the creation of John Mauchley and J. Presper Eckert, became famous when it was revealed in 1946. It was a giant machine, using over 17,000 vacuum tubes as binary switches (combined into racks so as to save time in searching for a single burnt out tube). Development had started in 1943 with US military funding. It was intended for calculating artillery firing trajectories but was Turing-complete and could be programmed to solve other problems. It was capable of holding a 10-digit number.
If the above interests you in any way I would highly recommend the 5-part BBC documentary series The Machine That Changed the World. It's one of those really high quality, well-researched and thoughtfully-paced programmes that are likely to be entertaining regardless of the subject material. You can watch it in its entirety on Youtube.