When it comes to buying gifts for children, everything is color-coded: Rigid boundaries segregate brawny blue action figures from pretty pink princesses, and most assume that this is how it’s always been. But in fact, the princess role that’s ubiquitous in girls’ toys today was exceedingly rare prior to the 1990s—and the marketing of toys is more gendered now than even 50 years ago, when gender discrimination and sexism were the norm.

In my research on toy advertisements, I found that even when gendered marketing was most pronounced in the 20th century, roughly half of toys were still being advertised in a gender-neutral manner. This is a stark difference from what we see today, as businesses categorize toys in a way that more narrowly forces kids into boxes. For example, a recent study by sociologists Carol Auster and Claire Mansbach found that all toys sold on the Disney Store’s website were explicitly categorized as being “for boys” or “for girls”—there was no “for boys and girls” option, even though a handful of toys could be found on both lists.

That is not to say that toys of the past weren’t deeply infused with gender stereotypes. Toys for girls from the 1920s to the 1960s focused heavily on domesticity and nurturing. For example, a 1925 Sears ad for a toy broom-and-mop set proclaimed: “Mothers! Here is a real practical toy for little girls. Every little girl likes to play house, to sweep, and to do mother’s work for her":

Such toys were clearly designed to prepare young girls to a life of homemaking, and domestic tasks were portrayed as innately enjoyable for women. Ads like this were still common, though less prevalent, into the 1960s—a budding housewife would have felt right at home with the toys to “delight the little homemaker” in the 1965 Sears Wishbook:

While girls’ toys focused on domesticity, toys for boys from the '20s through the '60s emphasized preparation for working in the industrial economy. For example, a 1925 Sears ad for an Erector Set stated, “Every boy likes to tinker around and try to build things. With an Erector Set he can satisfy this inclination and gain mental development without apparent effort. … He will learn the fundamentals of engineering”:

However, gender-coded toy advertisements like these declined markedly in the early 1970s. By then, there were many more women in the labor force and, after the Baby Boom, marriage and fertility rates had dropped. In the wake of those demographic shifts and at the height of feminism's second-wave, playing upon gender stereotypes to sell toys had become a risky strategy. In the Sears catalog ads from 1975, less than 2 percent of toys were explicitly marketed to either boys or girls. More importantly, there were many ads in the ‘70s that actively challenged gender stereotypes—boys were shown playing with domestic toys and girls were shown building and enacting stereotypically masculine roles such as doctor, carpenter, and scientist:

Although gender inequality in the adult world continued to diminish between the 1970s and 1990s, the de-gendering trend in toys was short-lived. In 1984, the deregulation of children’s television programming suddenly freed toy companies to create program-length advertisements for their products, and gender became an increasingly important differentiator of these shows and the toys advertised alongside them. During the 1980s, gender-neutral advertising receded, and by 1995, gendered toys made up roughly half of the Sears catalog’s offerings—the same proportion as during the interwar years.