Clustering is probably not a familiar term to most genealogists. Cluster research is a methodological system devised to identify an elusive ancestor based on expanding the focus of a search to a broader area either geographic or by subject and then doing more research to eliminate unlikely possibilities until the remaining individual or appears as the only possible correct choice.
Because this is a complicated topic, it is only rarely mentioned in genealogical writings and almost never discussed in conferences or workshops. In a sense, it is the last resort for resolving very difficult genealogical "brick walls." Surprisingly, there is a Wikipedia article on the subject entitled "Cluster genealogy." See https://en.wikipedia.org/wiki/Cluster_genealogy. However, the only contribution of the article to an understanding of the subject is the definition of a cluster:
A person's cluster consists of the extended family, friends, neighbors, and other associates such as business partners.A relatively few genealogists, seemingly independently, develop techniques for advancing their research using the principles of clustering even when what they are doing is not identified with that term. I find the most coherent explanation for this method of research in a book published back in 1972 entitled as follows:
Jones, Vincent L, Arlene H Eakle, and Mildred H Christensen. Genealogical Research; a Jurisdictional Approach. Salt Lake City: Printed by Publishers Press for Genealogical Copy Service, Woods Cross, Utah, 1972.
This book was reprinted with the following unlikely title:
Jones, Vincent L, Arlene H Eakle, Mildred H Christensen, and Genealogical Institute. Family History for Fun and Profit. Provo, Utah: Printed by Community Press for the Genealogical Institute, 1972.
In these books, the basic concepts of cluster research are referred to as a "jurisdictional approach." The basic concept of the process, no matter what it is called, involves expanding your research to include all of the possible records in a particular "jurisdiction" or geographic area. Genealogically important or relevant records are created at or near the time of an event by individuals or entities that have an interest in the event or have a duty or obligation to record the event. As I have written many time before, these records pile up in jurisdictional levels, i.e. national records, state or provincial records, county or parish records, municipal or town records and personal records like pancakes in a stack. Each jurisdictional level creates its own unique records such as the following examples:
- National level -- Military, tax, census, trade and commerce records
- State or province -- In the U.S. these could be, depending on the time period, birth and death records or records created by state agencies such as court records
- County or parish -- Can be birth, marriage and death records. In the U.S. also land and property records
- Municipalities or towns -- Local school, church, fraternal organizations and other records
- Personal records -- Diaries, Bibles, journals, letters etc.
Cluster research involves taking the routine searching of records and expanding the scope to include any possibly related individuals. I wrote about this about a year ago in a post entitled, "How does geographic clustering work?" See http://genealogysstar.blogspot.com/2015/12/how-does-geographic-clustering-work.html. This explanation focuses on geographic clustering but it could also be expanded to include other classifications of clusters based on other types of records. In this case geographic proximity is the chief factor in determining relationships, but other records sources such as fraternal organizations, church records, and other similar records can also be used to advantage.
Some of the researchers who utilize cluster research use spreadsheets to compile information, others use maps and lists. Whatever personal method you use, the concept is the same: gathering a broad spectrum of information and then analyzing the information to separate individuals and hopefully, finally determining which of all possible candidates is the elusive ancestor.