George B. Grant (1849-1917) invented his first calculator in 1871 and exhibited it at the 1876 Centennial Exhibition. It was eight feet long and five feet high, weighed 2,000 pounds, and had 15,000 parts ?perhaps the largest calculator in history. Grant subsequently designed arithmetic calculators and adding machines. This calculator, manufactured by the Grant Calculating Machine Company of Lexington, Mass., was an improvement on the original Grant machine.