In the early 1980's, there was growing interest in building the various branches of the Casselman Family into a Casselman Ancestral Society. This desire was strongest in the old Loyalist Townships of Eastern Ontario where eight members of several Casselman families were granted land as United Empire Loyalists (UELs).

The Society was charted in 1986 under the Ontario Historical Society. The aim of the C.A.S. is to study and publish the history and genealogy of Casselmans (any variant of the name) and their relatives. The Society is historical, genealogical, charitable, social and non-profit in nature.

The activities of the Society involve holding family gatherings, conducting research into history and genealogy. Monies raised from volunteer membership and from publishing research reports can then be used to support the hosting of special events or to conduct further research and to publish additional genealogical information.

Activities include researching cemeteries, mottoes, and coats of arms; conducting tours to historic sites; hosting and participating in social events, such as, family reunions, picnics and special commemorations which promote greater understanding; publishing family newsletters; promoting good fellowship among members; and co-operating with other organizations, when the opportunity arises, to make others aware of the mission and activities of the Casselman Ancestral Society.