A member of the Quaker religious sect, he broke with the Society during the conservative reform movement and sponsored important legislation promoting military preparations for the French and Indian War.
However, Nathaniel remained in the Assembly and helped draft the bill that established guidelines for the use of privately owned wagons and horses to transport military supplies.
[1] In 1758, the Philadelphia Yearly Meeting condemned this bill as essentially repugnant to that liberty of conscience for which early Friends deeply suffered.
For example, in 1756 William Smith’s "A Brief View of the Conduct of Pennsylvania" charged that Grubb declared after hearing the news of the attacks on frontier inhabitants that "they are a pack of insignificant Scotch-Irish, who, if they were all killed, could well enough be spared.
In 1755, he was appointed as a commissioner to provide for the Arcadian exiles in Philadelphia and three years later served as a Trustee of the Province Loan office.
In addition to his mill on Crum Creek, he also owned property in Marcus Hook and several houses and lots in Philadelphia, which apparently he rented to tenants.