Boolean Logic
1848
George Boole developed an algebraic system of logic. He considered systems of logic where the variables were represented by the values of 1 and 0. Boolean algebra was essential to the study of circuit design by which computers were developed. Boolean logic is critical to the search strategies used on computer systems.

Illustration from:
"Mr. Boole's Theory of the Mathematical Basis of Logic," Mechanics' Magazine, vol. 49, 1848.