Authorized on April 23, 1775 in the Massachusetts State Troops as Gardner's Regiment. Elements continued in the county as 1st Middlesex County Regiment as depot and for local defense. The regiment consisted of eight companies, and was to have a total strength of over 700 men. Each company was commanded by a captain, and consisted of 76 privates, 4 corporals, 4 sergeants, 1 ensign, 2 lieutenants, 1 fifer and 1 drummer. Soldiers enlisted for one year. The regiment was organized in spring 1775 at Cambridge to consist of 10 companies from southeastern Middlesex County and Suffolk County. Adopted on June 14, 1775 into the Continental Army and assigned to the Main Continental Army. It was assigned to the on July 22, 1775 to Greene's Brigade, an element of the Main Continental Army. Consolidated (less Craft's Company) on January 1, 1776 with Mayhew's Company, Cotton's Regiment and Epery's Company, Danielson's Regiment and consolidated unit re-designated as the 25th Continental Regiment, an element of Greene's Brigade to consist of 8 companies; concurrently Craft's Company re-organized and re-designated as Craft's Company, 24th Continental Regiment.

Reassigned on April 15, 1776 from Main Continental Army and assigned to the Canadian Department. Reassigned on July 2, 1776 from Canadian Department and assigned to the Northern Department. It was assigned to the on July 20, 1776 to Arnold's Brigade, an element of the Northern Department. Arnold's Brigade re-designated 26 October 1776 as Poor's Brigade. Reassigned on November 26, 1776 from Poor's Brigade and assigned to Vose's Brigade, an element of the Main Continental Army. Vose's Brigade re-designated on December 18, 1776 as McDougall's Brigade. Consolidated (less Mayhew's Company) on January 1, 1777 with the 24th Continental Regiment and consolidated unit re-designated Greaton's Regiment; concurrently Mayhew's Company re-organized and re-designated as Warren's Company, Alden's Regiment.