An agricultural society is the nonprofit, often chartered more than a century ago, that owns a fairgrounds and runs the fair on it. It hires judges, prints the premium book and maintains the grandstand and exhibition hall between fairs. The Essex Agricultural Society runs Topsfield Fair, the Barnstable County Agricultural Society runs the Barnstable County Fair, and the Franklin County Agricultural Society runs the Franklin County Fair. A Grange is a different kind of organizer: a farm fraternal order, and the South Middleborough Grange Fair is run by one.
Agricultural society
The chartered nonprofit that owns a fairgrounds and runs the fair.
See it at these Massachusetts fairs

Shown first
AgriculturalFamilySeasonal
Topsfield Fair
Eleven days of livestock, rides, and giant pumpkins.
Oct 2–12Topsfield
EndedAgriculturalFamilySeasonal
Barnstable County Fair
A full week of rides, concerts, and animals on Cape Cod.
Date not confirmedFalmouth
EndedAgriculturalFamilySeasonal
Franklin County Fair
A Pioneer Valley fair since 1848 with the Roundhouse exhibit hall.
Sep 10–13Greenfield
EndedAgricultural
South Middleborough Grange Agricultural Fair
One-day Grange fair in South Middleborough, judged flowers, produce, preserves, and needlework.
Date not confirmedMiddleboro