In 1988, CamelBak founder Michael Eidson was competing in the "Hotter 'n Hell 100" bike race in Wichita Falls, TX. Eidson, who was an EMT by trade, filled an IV bag with water and stuck it in a tube sock. He then pinned the tube sock to the back of his jersey, pulled the tube over his shoulder, and secured it with a clothespin.
Within a few months, Eidson began selling the first CamelBak product, the ThermalBak, which quickly became popular among cyclists.
Original bladder size was 60oz