Manuscript collections probably stand first in line among records least utilized in genealogical research. Two reasons for this could be:
Researchers do not know how to access manuscript collections.
Researchers do not understand the types of records found in manuscript collections.
The most common places to find manuscript collections are university libraries, historical societies and museums. After researching historical records in local archives and courthouses, you should determine where the personal papers people from the area are archived and if they your person of interest is listed in an index or card catalog. Much information about these collections can be gleaned from an online catalog. For example, the summary of this collection gives the details about documents that provide information about slaves: Guide to the Gail and Stephen Rudin Slavery Collection, 1728-1893.
The resources found among manuscript collections can fill in the missing details about the life of the former owner and the people who were enslaved. Below is a list of the most common records that mention the enslaved and former owner found among manuscript collections.
Account books: "Starting in the late 1840's, Thomas Affleck’s account books instructed planters to record depreciation or appreciation of slaves on their annual balance sheet. In 1861, for example, another Mississippi planter priced his 48-year-old foreman, Hercules, at $500; recorded the worth of Middleton, a 26-year-old top-producing field hand, at $1,500; and gave 9-month-old George Washington a value of $150." See The Messy Link Between Slave Owners And Modern Management(Forbes).
Bible records have been known to provide information about the birth of slaves.
Bills of sale can help you document the possible time of arrival or departure of an enslaved ancestor.
Church records may include both the names of owners as well as the enslaved.
Diaries & journals help you to understand what life was like from the perspective of the owner and they also contain information about family relationships and events in the lives of owners and enslaved.
Insurance records reveal policies that were written to insure enslaved people.
Letters and other correspondence among personal papers help you to understand the perceptions about slavery or Civil War. They provide information about people and events.
Day books can provide information about document births, deaths and dates of sales. Medical day books can give information about treatment for sickness or diseases.
Slave inventories among personal papers can reveal slave names, ages, occupation, and value.
Wills can help you understand how inheritances were divided or if enslaved people were sold to satisfy the debts of an estate.