Library of Congress Subject Headings, all of those ideas can be found
by searching for:
States - History - Civil War, 1861-1865
not know exactly what subject heading to use. That's where LOIS steps
in to give you some help. Let's stick to the Civil War example and look
at the results of a search. What would happen if you searched for War
Between the States?
you that the heading you searched for is not used. But it also tells
you what the correct subject heading is for this library (see the red
arrow?), and gives you the option of clicking on that heading instead.
Try doing that in one of those old fashioned card catalogs!