The first calculators were abacuses, followed by the slide rule (invented by William Oughtred in 1622), and then mechanical calculators in the 1900s. The first electronic calculators emerged in the 1960s, but were large and heavy because they required many transistors. It wasn't until the 1970s that integrated circuits made pocket electronic calculators possible. Most vintage pockets electronic calculators are a dime a dozen, with few...Continue Reading