To join the Colonial Dames, you have to be descended from an ancestor that fulfilled a certain role or held a certain position. For two out of the three Dames societies, the roles and positions considered to make an ancestor “eligible” depend on the ancestor’s colony of residence. If your ancestor is from Nantucket, things are about to get complicated…
For most of Nantucket’s colonial history, it was part of Massachusetts.
But between 1664 and 1691, it was part of New York. (There’s a good outline of the history here.) If your ancestor’s qualifying service occurred during that period, it likely falls under the eligibility guidelines for New York, not Massachusetts. You need to be careful to ensure that it meets New York eligibility and to make the proper notations when doing application forms.
On the plus side, if the service is prior to 1674, you’ll also qualify for the Holland Dames.