Frank Stephen Baldwin

Frank Stephen Baldwin (April 10, 1838 – April 8, 1925) was an American who invented a pinwheel calculator in 1875. He started the design of a new machine in 1905 and was able to finalize its design with the help of Jay R. Monroe who eventually bought the exclusive rights to the machine and started the Monroe Calculating Machine Company to manufacture it.

Shortly thereafter, he invented and patented the "Recording Lumber Measure". This device started him thinking about calculating machines and this point really marks the birth of the Monroe calculator. In the office of a life insurance company at St. Louis, he had seen an arithmometer, a calculating machine devised by Charles Xavier Thomas around 1820 and which, at the time, was the only mechanical desktop calculator in commercial production. To create a model based on his ideas he hired William Seward Burroughs I to perform the work in his machine shop, which he, with his father, had in St. Louis.