The original 1660s plan for Nantucket was for a proprietorship with ten shareholders. Each of these ten chose a full partner, making twenty shares. Then it was decided to take on additional “half-share men” with useful skills needed by the shareholders who moved to Nantucket. If ten half-shares had been granted, the number of full shares would have been 25, but in fact, fourteen half-share grants were made. This added seven full shares to the previous twenty for a final total of 27.
Shares entitled holders to homestead lots plus grazing rights on the Common and Undivided Land. The shares could be inherited, bought, and sold as whole shares or as fractions of shares. Over time, some individuals acquired multiple shares, while on the other hand, inheritance tended to divide shares up into complex fractions.
In 1714 the Proprietors decided to divide each share into 720 units known as “sheep commons” for an original total of 19,440 units.
Shareholders had the right to turn in their sheep commons for set-offs of private property. As they did so, the remaining Common and Undivided Land shrank accordingly until it exists only vestigially. At present the Town of Nantucket holds almost all the remaining sheep commons.