Revolutionary War
Meanwhile, events had moved from local agitations against the British crown to outright war. Early on, Trigg served in local militias, but he also represented Fincastle in the Virginia Conventions. These were five political meetings that started after Lord Dunmore, the governor of Virginia, had dissolved the House of Burgesses after its delegates expressed solidarity with Boston, Massachusetts, where the harbor had been closed by the British. Trigg was at the first convention in 1774 and was elected a delegate to the second convention in 1775, though he did not attend. He was elected to the third convention (July–August 1775), and did appear. He was also a delegate to the Fourth Convention (December 1775 – January 1776), but did not attend.
His other revolutionary activity at the time was as a member of the Fincastle County Committee of Safety, an outgrowth of the Virginia Committee of Correspondence. The Virginia Committee of Correspondence was formed on March 12, 1773, and requested each county to do the same. The British refused to address the issues that were of greatest concern to the colonists, and so the freeholders of Fincastle County met at the Lead Mines on January 20, 1775, forming a Committee of Safety in which Trigg was a member. They were one of the first to respond to the request of the Virginia Committee of Correspondence to form such a body. Committees of Safety basically served as provisional governments for their area. It was at this meeting that they drew up the Fincastle Resolutions, which was a precursor to the Declaration of Independence issued by the Second Continental Congress on July 4, 1776; Trigg was one of the signatories. The resolutions, addressed to the Virginia members of the Continental Congress, contained the boldest assertion of the grievances and rights of the American colonies. In February 1775, he wrote to his brother-in-law William Christian, suggesting they call another meeting of the freeholders to elect their delegates to the second Virginia Convention. With the news that William Christian was leaving with the Fincastle militia company to Williamsburg to fight, Trigg took over as chairman of the Committee of Safety. On October 7, 1775, they met to express their appreciation of Trigg, writing that "together with the most exemplary zeal and attachment to the liberties of your country, and your indefatigable industry in the service thereof, you merit and deserve our particular thanks."
In 1776, Cherokees entered the war with the aim of driving colonists from their lands, which meant the people living in southwestern Virginia were facing British-armed Cherokees. The members of the Committee of Safety met at Fort Chiswell on June 11, 1776, and drafted a letter to Oconostota and Attacullaculla, chiefs of the Cherokee nation, to meet with them and come to terms for a peace agreement. The letter mentions the colonists' dissatisfaction with Britain:
It is true that an unhappy Difference hath subsisted between the people beyond the great water, and the Americans for som [sic] years, which was intirely [sic] Owing to some of the great Kings Servants who wanted to take Our money without Our Consent, and otherwise to treat us, not like Children, but Slaves, which the people of America will not submit to.
Trigg was one of the signers of this letter. The conflict with the Cherokees was called the Christian Campaign (presumably from Col. William Christian's last name) and Trigg was the paymaster in 1776–1777. In 1777, he was tasked with making a list of men who swore allegiance to several militia companies. By May 1778, the inhabitants along the New River had either left or were ready to leave at a moment's notice, due to increased hostilities with the Shawnee in the area. William Preston, an officer in the militia, felt exposed on the frontier, but was reluctant to abandon his home "Smithfield", not only for the safety of his family, but also for the county records he safeguarded. Trigg was then leaving for his term in the General Assembly, and Preston urged him and the other delegate for a guard. When it was initially presented to the Governor's Council, Preston's petition was denied, but Trigg met several times with Governor Patrick Henry about Preston's situation and won another hearing with the Council. Trigg made three separate appeals in all before carrying his point. When the governor agreed to send a guard of twelve men and a sergeant, Trigg sent Preston the news and also told him of the Treaty of Alliance that was signed in France in February.