But these unsupervised boys also formed gangs that harassed the mentally ill, the handicapped and racial and ethnic minorities. Boys played an outsize role in the anti-Irish pogroms in 1840s Philadelphia, the brutal New York City draft riots targeting African-Americans during the Civil War and attacks on Chinese laborers in Gilded Age California. These children did not invent the bigotry rampant in white America, but their unrestrained upbringing let them enact what their parents mostly muttered.

Their sisters followed a different path. Girls were usually assigned more of their mothers’ tasks. An 8-year-old girl would be expected to help with the wash or other physically demanding tasks, while her brother might simply be too small, too slow or too annoying to drive the plow with his father. But despite their drudgery, 19th-century American girls still found time for tree climbing, bonfire building and waterfall-jumping antics. There were few pretty pink princesses in 19th-century America: Girls were too rowdy and too republican for that.

So how did we get from “democratic sucklings” to helicopter parents? Though many point to a rise of parental worrying after the 1970s, this was an incremental change in a movement that began a hundred years earlier.

In the last quarter of the 19th century, middle-class parents launched a self-conscious project to protect children. Urban professionals began to focus on children’s vulnerabilities. Well-to-do worriers no longer needed to raise tough dairymaids or cunning newsboys; the changing economy demanded careful managers of businesses or households, and restrained company men, capable of navigating big institutions.

Demographics played a role as well: By 1900 American women had half as many children as they did in 1800, and those children were twice as likely to live through infancy as they were in 1850. Ironically, as their children faced fewer dangers, parents worried more about their protection.

Instead of seeing boys and girls as capable, clever, knockabout scamps, many reconceived children as vulnerable, weak and naïve. Reformers introduced child labor laws, divided kids by age in school and monitored their play. Jane Addams particularly worked to fit children into the new industrial order, condemning “this stupid experiment of organizing work and failing to organize play.”

There was good reason to tame the boys and girls of the 19th century, if only for stray cats’ sake. But somewhere between Jane Addams and Nancy Grace, Americans lost track of their larger goal. Earlier parents raised their kids to express values their society trumpeted.