100 Mile & District Historical Society

100 Mile Ranch, British Columbia, Canada.

O'Fallon Illinois Historical Society Museum

O'Fallon, Illinois.

Oak Brook Historical Society

Oak Brook, DuPage, Illinois.

Oakfield Pioneer Heritage Society

Oakfield, Kent County, Michigan.

Oakland County Genealogical Society

Birmingham, Michigan.

Oakland County Historical Society

Pontiac, Michigan.

Oakland County Pioneer and Historical Society

Pontiac, Michigan. Research library containing manuscripts, photographs, printed materials and oral histories on the history of Oakland County. Also home of Pine Grove Museum, the former home of Governor Moses Wisner.

Oberlin Historical and Improvement Organization

Oberlin, Ohio.

Obion County Historical Society

Union City, Tennessee.

Ocean County Genealogical Society, Toms River, NJ

The purpose of the group is to provide a forum for people who are researching their family history. It allows us to be able to share our genealogical adventures and learn from each other. New members are always welcome no matter what their level of expertise and we are glad to help beginners. We meet in the Home Town Dairy Room found on the second floor of the Ocean County Library in Toms River.

Ocean County Historical Society

Toms River, New Jersey.

Ocean Springs Genealogical Society, Inc.

Jackson County, Mississippi.

Oconomowoc Historical Society

Oconomowoc, Waukesha County, Wisconsin.

Oconto County Historical Society

Oconto, Wisconsin. Maintains the Beyer Home Museum, a restored 1890s northern mansion.

Oelwein Area Genealogical Society

Oelwein, Iowa.

Offaly Historical and Archaeological Society

The family history research centre for the Irish counties of Laois and Offaly.

Ogemaw Genealogical and Historical Society

West Branch, Michigan.

Ogle County Genealogical Society

Oregon, Illinois.

Ogle County Historical Society

Oregon, Illinois.

Ohio Cemetery Preservation Society

An association dedicated to preserve and protect Ohio's most precious and endangered heritage resources -- our historic cemeteries and burying grounds. A primary goal of OCPS will be to increase the awareness and inestimable value of our cemeteries as sosurces of community and state pride and encourage groups and individuals to help preserve them as landmarks for future generations to learn from and appreciate.