Certified Genealogist (CG)
From Ancestry.com Wiki
C.G. is the abbreviation for Certified Genealogist.
The postnominal of C.G. is administered by the Board for Certification of Genealogists®. Applicants to become a Certified Genealogist must prepare a portfolio of work samples. Those who complete their certification are able to use the C.G. postnomial and are also listed in the BCG Certification Roster. Individuals can also earn the Certified Genealogical Lecturer credential.
Previously, the Board offered credentials of Certified Lineage Specialist (CLS), Certified American Indian Lineage Specialist (CAILS), and Certified Genealogical Records Specialist (CGRS), and Certified Genealogical Instructor (CGI). These credentials are no longer current, but you might see them in older publications.
To learn more about becoming a Certified Genealogist, you can purchase the BCG Application Guide.