The library uses the Library of Congress Classification System to organize our books. Many books on European history will have call numbers that start with the letter "D."
When you find a book in the library catalog, be sure to make a note of the call number before you head for the stacks, and be sure to check that the book is "available." Library staff are always glad to help you to locate a book in the stacks!
Here's a refresher on how to read LC call numbers from the Online Library Learning Center.