The collection “Black Biographical Dictionaries, 1790-1950,” is a major gathering of old biographical dictionaries containing more than 30,000 references. The entries record famous and historic, as well as average people. The 297 volumes, on 1070 microfiche range from listings of national activists, state and local personalities, women, professional directories, fraternal order members, church and missionary listings among others. This collection is widely available. The titles come from more than 100 public and private repositories across the United States and Great Britain. The compilers of this massive African American library include; Randall K. Burkett, Nancy Hall Burkett, and Henry Louis Gates, Jr. This source may be your first step in tying into your Irish line.
If a former slave ancestor is mentioned in these works, the chances of the owner or series of owners being mentioned is very good. For example, volumes 181-183 are Abigail Field Mott’s Biographical Sketches and Interesting Anecodotes of Persons of Color published in 1826, 1837 and 1839. These are descriptions of freed slaves or individuals from free families. The sketches frequently mention birthplaces, parents’ names, and former slave owners. This could very well connect you into an Irish slave master, who was also family.
This important collection is available on microfiche at many libraries and archives. There is a three volume index to this collection titled Black Biography, 1790-1950: A Cumulative Index. The first two volumes index biographical sketches alphabetically; volume three is an index by place of birth, occupation, religion and sex.
A second series supplements the dictionaries as new books have been identified. These also are indexed. Both the supplement and the index can be found at any number of university and academic archives.
Remember, what made a person worthy of a biographical sketch historically in the African American community, is different than in the white community.