1946: The ENIAC computer begins operating.
Below is an excerpt about the ENIAC from an article, "Top Intelligence Agency Supercomputers," by David Brown. Click the link at the end of the page to view the full article.
During World War II, the Army commissioned the first general-purpose electronic computer. Described to the press as a “giant brain” (how else would you describe a computer to a world that had never before seen one?), ENIAC cost $6 million in today’s dollars, weighed 30 tons and took up 1800 square feet, which is about the size of a house. Anecdotally, it used so much electricity to operate that each time it was switched on, it caused lights in Philadelphia to dim.
The system was developed to calculate artillery firing tables for the Ballistic Research Laboratory, but when scientists from the Manhattan Project found out about it, they co-opted the system to run calculations for the Bomb.
Read the full article via the link below.