The Bobbsey Twins was the longest-running children's book series in the twentieth century. From 1904 to 1992, over one hundred volumes about the two sets of Bobbsey twins appeared. The series won a large audience among children not quite ready for the Hardy Boys (see entry under 1920s—Print Culture in volume 2) or Nancy Drew (see entry under 1930s—Print Culture in volume 2) series of adventures.

Beginning with The Bobbsey Twins; or, Merry Days Indoors and Out (1904), the series depicted the adventures of two sets of twins: Freddie and Flossie Bobbsey and their older brother and sister, Nan and Bert. Especially in the early volumes, the adventures were fairly tame, usually involving travel to places like the seashore, the mountains, or a big city. The fair-haired Freddie and Flossie were four years old in the early books and then six years old in later...