McClary was born in Ulster, Ireland and came to colonial America with his parents at age sixteen where they lived on a farm in New Hampshire.

In the mid 1700s New Hampshire frontier McClary gained much of his field experience leading expeditions against hostile Indians in the area.

During the revolution he assembled a company of men in New Hampshire and marched over seventy miles to Boston and fought at the Battle of Bunker Hill.

McClary stood well over six feet tall, with a straight, proportioned and athletic build, with blue eyes and was known as a jovial and generous man.

His entries in the town books revealed a thorough knowledge of business and language and according to contemporary historian John C. French, exhibited a unique literary and writing style.

[1] In 1755 McClary led a company of soldiers in search of the Indians who massacred and took prisoners from the McCall family of Salisbury.

[7][8] In the months preceding the Revolutionary War it is said that McClary began to distinguish himself for his resolution and patriotism in planning and leading the attack of the castle at Portsmouth, New Hampshire, on December 1, 1774.

[10] On April 27, 1775, when word of the Battles at Lexington and Concord reached the Suncook Valley in New Hampshire, McClary was busy plowing land back on his farm.

After passing through Medford, they continued south and marched on Cambridge Common where upon arrival were all willing and eager to fight for the Revolution.

[12] On June 16 they received orders to join with American forces and prepare for battle at Bunker Hill, in Charlestown, across the Mystic River from Boston.

[13] During the first British advance on the American fortifications atop Breed's Hill, McClary, along with Seth Pomeroy, John Stark, James Reed and Thomas Knowlton, were at the front in the redoubt.

He was cautioned by his son and other men not to embark on such a risky effort, but McClary exclaimed, "The ball is not yet cast that will kill me!".

[22] McClary's body was taken to Medford, Massachusetts, just outside Boston near the encampment of the New Hampshire Brigade, along with other soldiers who died during the battle, and was buried with military honors.

It read: "The Major discovered great intrepidity and presence of mind in the action, and his noble soul glowed with ardor and the love of his country.

The tablet was secured through the efforts of the Epsom Historical Club, and is attached to a tall granite pillar, weighing approximately 5,000 pounds (2,300 kg).

[24] McClary's image appears in John Trumbull's famous painting of the Battle of Bunker Hill, where he is pictured raising his musket to shoot the British soldier attempting to bayonet the mortally wounded Warren.

Written by Warren Trip in "The McClary's of Epsom" is the following text:"He was a favorite officer, nearly six and one-half feet in height, with a Herculean form, a voice like Stentor and strength of Ajax, never equaled in athletic exercises and unsubdued in single combat.