On October 2, 1955, technicians at the U.S. Army's Ballistic Research Laboratory flipped the final switch on ENIAC, plunging its eighteen thousand glowing vacuum tubes into permanent darkness. Conceived during World War II to calculate artillery firing tables, the Electronic Numerical Integrator and Computer had operated almost continuously for a decade. While modern engineers often fixate on its colossal thirty-ton footprint and labyrinthine patch cables, ENIAC's true breakthrough was psychological: it proved that electronic speed could fundamentally outstrip human calculation. By the time it went silent, computing had already begun migrating from room-sized bespoke monoliths toward commercial architectures and the dawn of silicon transistors. Powering down ENIAC was not a defeat by obsolescence, but the computing world's first graduation ceremony, ushering humanity out of the fragile vacuum-tube era and into the exponential velocity of the digital age.