All books are assigned unique call letters which place books on the same subject together on the shelves. Collier Library books have Library of Congress call letters which always have one or two letters on the first line. You can examine an outline of the Library of Congress Classification System, to see which letters are assigned to subjects of interest to you.
The Collier Main collection is located on the second and third floors. Books from this collection with a call letter starting with a letter A through M are located on the second floor. Books having a call number beginning with N through Z are shelved on the third floor.