These photos reveal how America's definition of the $20.4 billion 'plus-size' market has changed over the years

The brand - which once advertised "slenderizing" clothing for "stout" woman - has transformed into one of the leaders in advertising that puts body positivity front and center. 

Lane Bryant's transformation is driven by a shifting culture and growing customer base. The plus-sized clothing market is estimated to exceed $20 billion. According to a Lane Bryant investor presentation from early 2017, the brand believes that figure could reach $40 billion to $50 billion. 

"There is, to put it crudely, an insane amount of money just sitting on the table, and it seems, finally, that there are some savvy entrepreneurs out there ready to shrug off fashion's inherent snobbery and claim a piece of it," Ashley C. Ford recently wrote in New York Magazine.

Here's how Lane Bryant's transformation shows just how much the definition of plus-sized has changed over the last century.