When was the spiral notebook invented?

There's no single inventor or date for the spiral notebook. The concept of binding papers together with a spiral mechanism evolved gradually over time. While specific patents exist for various spiral binding mechanisms, it's difficult to pinpoint a single "invention" date for the common spiral notebook as we know it. The widespread adoption and popularization of spiral notebooks likely happened in the late 19th and early 20th centuries, with improvements in manufacturing techniques making them more affordable and accessible.