This ad for a correspondence school appeared in a magazine in 1916. We don't know how accurate it is (after all, it's advertising), but it couldn't be too wildly off for its intended audience. According to the post at Ptak Science Books, the average wage earner in 1916 was making about $650 a year.
If you made more than $10K a year back then, you were in the elite category! And the same as today, it's more useful to figure the starting point of the top bracket (the 1%) rather than the average because there's no upper limit on the amount of money someone can make, which throws off averages. The post also takes a look at baseball player's salaries then and now. Things really have changed in 97 years! -via Carl Zimmer