There were two broad categories of troops involved on the US side, the Continental Army and the militias. One common mistake people make, largely due to the pedagogical tendency to heavily emphasize the Battles of Lexington and Concord, is the conflation of the two.

The Continental Army was a genuine attempt of the fledgling government to have a regular army, with men signed up for enlistment periods of one and later three years (in contrast to 21 years or lifetime service in the British army). It was directly overseen by the Continental Congress. The militias consisted of whomever could be scraped up for short term duty and were organized by colonial/state governments to varying capacities. Shortfalls often meant that the Continental Congress had to provision these units as well. In general, with a few exceptions, the militias were useless for anything but basic security work, as equipment sent their way tended to be looted (what do you think a poor farmer is going to do when handed a shiny new musket on the government's dime?) or rendered inoperable due to neglect and improper maintenance. Their purpose was primarily morale, to ensure a broad base of participation and legitimacy. This has been amplified in the post-Revolution mythmaking that persists to this day.

So to answer your question succinctly, there were large numbers of "farmers with pitchforks and muskets," but they were generally not doing the heavy lifting when it came to fighting. That was the job of the trained regular troops of the Continental Army.

• Hugh Jameson, “Equipment for the Militia of the Middle States, 1775-1781,” The Journal of the American Military Institute 3, no. 1 (1939): 26-38.
• Robert Reinders, "Militia and Public Order in Nineteenth-Century America," Journal of American Studies 11, no. 1 (1977): 81-101.

To quote Reinders: "In the popular mind the militia has been given a romantic patina - the image of Cincinnatus leaving his plow, taking up his flintlock rifle from over the cabin fireplace and joining his neighbors to fight the French, Indians, British, Mexicans and Spaniards - all merged with folk memories of Minutemen and ‘Davy’ Crockett and ‘Andy’ Jackson, while ignoring the truer picture of a staggeringly inept force."