Her father was the scion of a prominent Memphis family, her mother a dancer with dashed Broadway dreams. A typical outfit, Brody reports, was a Brooks Brothers suit with combat boots and a cape. In her bluejeans, old sneakers, and fake glasses, Harriet takes after her inventor, characterized by the poet James Merrill as a “bright, funny, tiny tomboy.” At four feet eleven, Fitzhugh was sometimes mistaken for a child, and she dressed in boys’ or men’s clothing throughout her life. She carries around a composition notebook filled with brutal observations about her classmates and neighbors, many of whom she follows on her “spy route.” Peering into windows and crawling into dumbwaiters, she tails her subjects: the bickering family in charge of the local grocery store, the dedicated birdcage builder who spoils his cats, the widow who believes that lying in bed is the secret of life. In “ Sometimes You Have to Lie: The Life and Times of Louise Fitzhugh, Renegade Author of Harriet the Spy,” published last year, the biographer Leslie Brody argues that Fitzhugh put forward “an entirely new and radically different version of the American girl.” Harriet is an intrepid eleven-year-old spy who lives on Manhattan’s Upper East Side with her parents and her beloved nanny, Ole Golly.

That’s a story that can be filled in with a look at the life of her creator. (There are no cell phones, but Harriet’s prep-school class is multiracial, and any dated features of the source material have been excised.) As the rebellious tomboy is revived for an audience unlikely to see her as especially gender-bending, it’s easy to lose sight of what she meant in her own time. Animation lends itself more readily to the blurring of time periods than live action does, and a new cartoon Apple TV+ adaptation, starring Beanie Feldstein, could be set at any point in the past half century. In 1996, Nickelodeon transported her out of the mid-century, with a goofy live-action film starring Michelle Trachtenberg. Take, for instance, the nineteen-sixties’ most iconic underage sleuth, Harriet M. Stripped of their initial contexts, and cleansed of any outdated particularities, they seem to endure in an eternal present tense. There is a certain alchemy by which canonical characters, especially the figures of children’s literature, come to exist outside of history.

Harriet the spy books in order