Invention Begins at Forty:

This paper examines a group of prolific women inventors, all specializing in machines, and all arguably professional inventors for some or all of their working lives. The group is interesting in its very existence, which contradicts time-honored stereotypes against woman as inventors, and especially as professional inventors. However, it is particularly interesting for its high average age at first patent and its continuation of patent and/or inventive activity into old age. Data on the women's marital and economic status and social class are presented where available, and the group is compared with a sample of nonprofessional women inventors who exhibited at the Philadelphia Centennial of 1876.