To find regimental histories in the Musselman Library Collection:
This will return over 800 results. You can narrow down your results several ways. One method is adding a keyword to your search. For example, you could perform the original search and add a state (e.g. Virginia). The Virginia example reduces the results to about 130. You could also add keyword searches for regiment numbers, authors, or Civil War figures.
You can also narrow your results by performing the original search and using the left-hand menu to refine your search. For example, you could limit your results to books:
Limit by publication date:
Or limit by subject: