After attending local public schools, he became a clerk in his father's trading house, but the growing rift between the colonies and Great Britain quickly thrust Gilman into the struggle for independence.

A superb combat officer, Scammell made good use of Gilman's administrative talents in the task of creating a potent fighting force out of the limited manpower resources at hand––a combination of raw recruits from around the state and ragged veterans of the Trenton-Princeton campaign.

Because New Hampshire lay along the major invasion route from Canada to New York, Washington assigned its regiments a key role in the strategic defense of the northern states.

In the spring of 1777 Gilman and the rest of the officers and men of the 3rd New Hampshire marched to Fort Ticonderoga on Lake Champlain to participate in an attempt by American forces to halt the advance of a powerful army of British and German regulars and Indian auxiliaries under General John Burgoyne.

The veteran British troops outflanked the fort, and only at the last minute did the garrison, including the 3d New Hampshire, escape capture by making a dangerous night.

The American retreat lasted through the early summer until a combination of British transportation difficulties and delaying tactics employed by the Continentals finally slowed the enemy advance.

This delay allowed time for a mass mobilization of New England militia, including a New Hampshire Regiment of volunteers led by John Langdon and Gilman's father.

That winter encampment put the units of the Continental Army to their supreme test, a time of suffering and deprivation from which they emerged as a tough, professional combat team.

His duties in carrying out the myriad tasks necessary to keep a force in the field placed him in daily contact with Washington, Baron von Steuben, Henry Knox, Nathanael Greene, and others.

He personally saw action in the remaining battles fought by Washington's main army, including Monmouth and Yorktown, while continuing to hold his captain's commission in the New Hampshire Line.

Although he was unable to attend, his selection recognized Gilman's emergence as a nationalist spokesman since the convention had been called specifically to address the country's serious economic problems and the inability of the separate states or Congress to solve them.

Although he and fellow New Hampshire delegate John Langdon, his father's former commanding officer, reached Philadelphia after the proceedings were well under way, they both immediately joined in the debates and helped hammer out the compromises needed to produce a document that might win approval in every state and region.

He called the new supreme law of the land "the best that could meet the unanimous concurrence of the States in Convention; it was done by bargain and Compromise, yet, notwithstanding its imperfections, on the adoption of it depends (in my feeble judgment) whether we shall become a respectable nation, or a people torn to pieces ... and rendered contemptible for ages."

Those words typified Gillman, but his modesty failed to mask the justifiable pride he obviously felt in the accomplishment of the Founding Fathers in which Gilman had played no small part.