With more than 3.1 million views to date, “Night of the Living Dead” is among the most popular feature films on the Internet Archive. The 1968 movie is also generally acknowledged as one of the landmark films of the horror genre, as well as the work that single handedly created the modern conception of the zombie. But none of that would have been possible without a mistake—one that landed the film firmly in the public domain.

Legends about zombies date back to 19th-century Haitian folklore, and originally featured corpses (or even living people) that were enslaved by powerful sorcerers. However, George Romero—who co-wrote and directed “Night of the Living Dead”—created something quite different for his film. Romero’s monsters were cannibals who craved human flesh, serving nobody and nothing except their mindless hunger. They were victims of disease, transformed by being bitten, whose sudden appearance caused entire societies to collapse. In fact, these creatures were so unique that the movie never even called them “zombies”—Romero referred to his creations as “ghouls.”

At one point, this innovative work-in-progress with its innovative monsters was called “Night of the Flesh Eaters,” but the production company decided to change the title to avoid confusion with a preexisting film. The title card was switched to rename the film “Night of the Living Dead,” accidentally omitting the copyright symbol in the process. Under US intellectual property law at the time, the film immediately entered the public domain. Not only could the film be legally copied, shared, and redistributed—which led to its rapid dissemination through American pop culture—but anybody was free to adapt, change, or borrow from it.

What followed was not only a revolution within the horror genre, but an explosion of zombie-related content. “Night of the Living Dead” spawned nine direct sequels and several unofficial ones, as well as hundreds of works taking advantage of an uncopyrighted new monster. Works ranging from “The Walking Dead” to “World War Z,” “Pride and Prejudice and Zombies” to “Game of Thrones,” or “Resident Evil” to “Shaun of the Dead” all rely on Romero-type zombies or their derivatives.

Zombies dominate pop culture like few monsters have before or since, in large part because artists and authors can reuse, remix, or adapt them without fear. Night of the Living Dead is a shining example of what happens when quality works come into the public domain, joining the marketplace of ideas. If you want to watch this cinematic masterpiece for yourself, download or stream it here!