The was created by Melvil Dewey in 1873 and is still used by libraries today to organize their collections. The DDC strives to assign all the knowledge in the world to 10 different topical areas organized by number so that each range of numbers (starting with 000–099) is assigned a broad topic area. Below is an outline of these topics.
000–099: Computer Science, Information and General Works
100–199: Philosophy and Psychology
300–399: Social Sciences
700–799: Arts & Recreation
900–999: History & Geography
These 10 broad topics are then subdivided into 10 more specific topics. As an example, the 900s–History & Geography is divided below.
910–919: Geography & Travel
920–929: Biography & Genealogy
930–939: History of the Ancient World (to ca. 499)
940–949: History of Europe
950–959: History of Asia
960–969: History of Africa
970–979: History of North America
980–989: History of South America
990–999: History of Other Areas
And then these get broken down even further! Let’s look at the 970s.
970: History of North America
972: Mexico, Central America, West Indies
973: United States
974: Northeastern United States
975: Southeastern United States
976: South Central United States
977: North Central United States
978: Western United States
979: Great Basin & Pacific Slope region
When we look at this book that we found with OneSearch, we can see that its Dewey number is in the 900s. That means it is part of History & Geography. Specifically, it is a 973, which means it is about History of North America–United States. The .3 refers to the time period between 1775 – 1789.
A type of library classification system that organizes books using 10 main classes. Each of the 10 classes have a hierarchical system of subclasseses that become increasingly more specific.