In the 1760's, a dispute with the colonial government in neighboring New York ultimately led to an end to Wentworth's land grants, and he eventually stepped down as governor in 1766.

[1][3] After the apprenticeship, his father arranged for Wentworth to work as a merchant, plying the colonial trade with the West Indies and Spain in timber, wine and brandy for about a decade.

After his father died in December 1730, Wentworth, who had not acquired any property in Boston, returned to Portsmouth to assume control over his inheritance, including 2,000 pounds, extensive real estate, and the family trade in ship masts and timber.

[6] Prior to this occurring, Belcher and Waldron had ousted his family from positions of political authority, which led Wentworth to conspire with fellow politician Theodore Atkinson to remove the two from power.

[1][9] After British settlers established the Province of Georgia in 1732, Anglo-Spanish relations quickly deteriorated, and in 1733 the Spanish government refused to pay Wentworth for a shipment of timber worth 11,000 pounds.

This refusal put Wentworth at the mercy of his creditors in Boston, and he was forced to borrow heavily from British merchants in London, in particular associate John Thomlinson, to pay them off.

Under the influence of Atkinson, who sat on the commission, its members eventually decided to issue a ruling in support of New Hampshire's boundary claims, doubling the size of the nascent colony.

Eventually, Thomlinson (who held political influence due to Thomas Pelham-Holles, 1st Duke of Newcastle being his patron) formulated a plan where in exchange for 300 pound sterling, Wentworth would be appointed as the governor of New Hampshire; in return, he would drop his ongoing claim against the British government.

Wentworth primarily concerned himself in office with issuing land grants, placating potential rivals by issuing them with justice of the peace and military commissions, and appeasing the timber industry by turning a blind eye to the controversial white pine laws, allowing merchants free access to the New Hampshire forests in order to cut down white pine trees so long as they kept supplying masts to his brother Mark, who sold them to the British Royal Navy.

Wentworth joined them in the early-1740's and supported the Society for the Propagation of the Gospel, a missionary arm of the Church, by issuing them several land grants on the North American frontier.

His nephew John, who had prevented Wentworth from being dismissed in disgrace due to his political relationship with Charles Watson-Wentworth, 2nd Marquess of Rockingham, assumed the governorship of New Hampshire the next year in 1767.

He was described by American historian David E. Van Deventer as being "able to [both] maintain a family dynasty and Portsmouth's control of the prosperous mast trade for a generation" who was "perhaps even British America's first political machine.

Angered that his family had shunned him over marrying someone who was socially beneath him, Wentworth gave his estate in its entirety to Martha in his last will and testament, leaving them nothing.