The first bread slicing machine was invented by Otto Frederick Rohwedder of Davenport, Iowa, USA in 1912.
(His first machine was destroyed in a fire, but he got another machine up and working in 1928 and the first commercially sold slices were sold by the Chillicothe Baking Company of Chillicothe, Missouri, who produced their first slices on July 6th. Nowadays we call any good idea of invention "the best thing since sliced bread".)