score:4
From Laird's Advertising Progress: American Business and the Rise of Consumer Marketing:
[The branding and advertising pioneer J. Walter Thompson] enhanced the value of advertising in "better" magazines and made an important, albeit coarse, step towards segmenting the population into markets defined by characteristics other than geography, ethnicity, or population.
A whole chapter of this book is called "Early Advertising Specialists". I can't see all of its contents here, but the details you want are almost certainly in there.