Whether it’s the deep tones of magenta or barely tinted carnation, the color pink is, for better or for worse, associated with femininity. This wasn’t always the case. In fact, it was once the opposite.

In 1918, an article from a trade publication called Earnshaw’s Infants’ Department, declared that, since it was derived from red, “Pink is for the boys, and blue for the girls. The reason is that pink, being a more decided and stronger color, is more suitable for the boy, while blue, which is more delicate and dainty, is prettier for the girl.”

So when did this change?

To some extent, the shift happened after WWII. “Rosie the Riveter (a cultural icon who represented the American women who worked in factories and shipyards) traded in her factory blues for June Cleaver’s (popular American sit-com actress) pink apron,”. “Femininity got wrapped in pink, and so did products—from shampoos to fancy fashion.”

Indeed, the ‘50s and ‘60s are full of pink moments, from the strawberry-colored Chanel suit to Marilyn Monroe’s hot pink strapless dress from Gentlemen Prefer Blondes.

But Jo B. Paoletti, historian and author of Pink and Blue: Telling the Girls From the Boys in America, believes the line was firmly drawn in the 1980s, when two things happened. First, it became more and more common for parents to find out the gender of their children while they were still in the womb. Excited moms and dads wanted to buy gender-specific items for their new little bundles of joy, and of course, retailers obliged.

The other main reason, Paoletti theorizes, is because mothers who grew up wearing gender-neutral clothes and playing with toys that appealed to both boys and girls wanted their daughters to be able to revel in pink, lace, long hair, and Barbies. Marketers and advertisers just made this choice seem natural.

When you look at the big picture, the “pink is for girls” trend is a fairly recent one. It may not be long before the controversial pink- and blue-tinted aisles at big box stores have been replaced by some other shade entirely.