In the American Revolutionary War units of the Continental Army were assigned to any one of seven regional or territorial departments to decentralize their command and administration. This was necessary because the regiment was the largest permanent unit in the Continental Army. A superior headquarters, above regiment, was needed if more than a few regiments were stationed in the same department. Although brigades, divisions, and field armies existed, they were temporary units which did not necessarily include all the units assigned to a department. Nor did field armies include establishments of the staff, such as magazines (supply depots) of the Quartermaster General's Department, or hospitals of the Hospital Department. The militia in a department was usually at the disposal of the department commander.
Departmental organization
The Continental troops in a department constituted its garrison. If the garrison was sufficiently large, the units might be assembled into a field army. In this case the commander of the territorial department and the commander of the field army would be one and the same officer. Thus, the commanding general of the Northern Department was also commanding general of the Northern Army, and the commanding general of the Southern Department was also commanding general of the Southern Army. Armies did not, however, invariably receive a geographical designation. Because the field army under Washington's personal command contained the majority of Continental Army units it was designated the Main Army. Each department had a semi-autonomous commanding officer, usually a commanding general, under the overall command of Washington as General and Commander-in-Chief. The Continental Congress dealt with and through the department commanders.
Appointment of department commanders
Throughout the war, the Continental Congress retained exclusive authority to appoint or remove department commanders. In practice, when an urgent need arose, a temporary commander was just as frequently appointed by George Washington or the executive power of one of the states, pending the approval of the Continental Congress. Many of these temporary department commanders were then confirmed and formally appointed by the Congress. This practice, along with control of the Continental Army and Navy through the war and marine committees of the Continental Congress, established the precedent for civil control of military affairs later embodied in the Articles of Confederation and the United States Constitution.
Relations between the departments and the states
The department commanders and their staffs also worked directly with the governments of the states within their department. At first these were the ad hoc provisional governments developed in 1774 and 1775, but the practice continued after 1776 when the states replaced their Provincial Congresses and Conventions with permanent governments operating under written constitutions. Ordinarily departments were commanded by major generals. Washington as a full general was the ranking general officer in the Continental Army throughout the war.
Departments
In general there were seven territorial departments, although their boundaries were subject to change and they were not all in existence throughout the war.
Canadian Department
The establishment of the Canadian Department reflected the aspirations of the Continental Congress and some Americans to annex the British province of Quebec, then often referred to as "Canada", but the effort was ultimately unsuccessful. Although the Americans captured Montreal in November 1775, and established their headquarters at Château Ramezay, the region was never entirely under the control of the Continental Army. The Canadian Department was formally established from the New York Department on January 17, 1776.
Eastern Department
The Eastern Department was formed around those states that had originally sent troops to support the Siege of Boston, and in that sense it even existed before the Continental Army.
This was essentially the New England department, and included the states of New Hampshire, Massachusetts (including the present state of Maine), Rhode Island, and Connecticut. For the first year of the war, the field army associated with this department, under the command of General Washington, was variously designated as the Continental Army, Grand Army, or Main Army. The Eastern Department was formally established on April 4, 1776 when the Main Army under Washington moved from Boston to New York City. Important operations in this department included the Siege of Boston in 1775–1776 and the Battle of Rhode Island in 1779. The department was discontinued in November 1779.
Northern Department
The predecessor of the Northern Department was the New York Department, which was established on June 25, 1775. This department was sometimes described as the Separate Department The original New York Department was coextensive with the Province of New York. The department's boundaries were extended to include Canada in the initial phase of the Invasion of Canada, but Canada was established as a separate department on January 17, 1776. When the Middle Department was created on February 27, 1776 the New York Department was merged into it. The Middle Department, as originally organized, included all of the colonies of New York, New Jersey, Pennsylvania, Delaware, and Maryland. The inclusion of New York in the Middle Department continued for less than two months, however. In April 1776 the Main Army moved from Boston to New York City and Washington assumed command of the Middle Department. The Northern Department was formally established from the Middle Department on April 14, 1776. The reorganized Northern Department included only that portion of the colony of New York north of the Hudson Highlands, and the present state of Vermont. Operations in this department did not end with Saratoga. Fighting continued in the Northern Department until the end of the war. The department was discontinued upon the death of its last commander, General Alexander, at Albany on January 15, 1783. The British sought to gain control with the Saratoga campaign in 1777, and frequently raided into the southern reaches of the department to interfere with the movement of military goods and personnel. One of the most notable incidents in the history of this department was the defection of Benedict Arnold in September 1780.
Middle Department
The Middle Department was established on February 27, 1776.
Western Department
The Western Department covered the frontier territories west and northwest of Virginia and Pennsylvania, including the present states of Ohio, Indiana, Illinois, Michigan, and Wisconsin. It extended from Pittsburgh all the way to the Illinois country and as far north as the southern peninsula of Michigan. The department was established in 1777. Its first commander was Edward Hand. George Rogers Clark's Illinois campaign of 1779 was one of the most notable operations in this department. This department was the only one to remain after the war. The last elements of the Continental Army, stationed at Fort Pitt, were kept to guard the western frontier outposts.
Southern Department
The Southern Department was formally established on February 27, 1776. The Southern Department existed until the close of the war.