Answered By: Deborah Kelley-Milburn Last Updated: Jul 15, 2015 Views: 87
Widener used its own unique classification system until 1977 when we switched to Library of Congress. At that time, we did not convert the millions of old records to LC, so now we have materials in both classifications.
Many Harvard libraries which now employ commonly used classification systems like the Library of Congress' had their own systems at some point, so you'll often find Harvard libraries with two classification systems. The Countway Library of Medicine, for instance, has the Boston Medical Library classification system and the currently used National Library of Medicine system.