From the 1800s, Americans increasingly used numbers to make calculations in their heads that they used to describe the world around them. Schoolchildren learned to do basic arithmetic with paper and pencil. Objects such as slates, first found in the classroom, came to be owned by individuals.
Aids for Commerce and Consumers
Beginning in the 1880s, business and government employees across the nation calculated with machines. Some operators received special training from vendors, while others learned on the job. Especially from the 1920s, consumers also purchased relatively inexpensive, portable adding machines.