First Middlebrook Encampment

"Middlebrook encampment" may refer to one of two different seasonal stays of the Continental Army in central New Jersey near the Middlebrook in Bridgewater Township in Somerset County. They are usually differentiated by either the date of the encampment or their chronological order (First vs Second).
The First Middlebrook encampment refers to the spring encampment of the Continental Army, commanded by General George Washington, during the American War for Independence near the Middle Brook in Bridgewater Township, New Jersey (between Martinsville and Bound Brook) in 1777. The second, longer winter cantonment took place in 1778–1779, from December 1 to mid-June. A cantonment is a protracted quartering of an army in a specific location, typically for the duration of the winter.

A portion of the first encampment site, known as the Washington Camp Ground, was added to the National Register of Historic Places on July 3, 1975. The Campground is located in Martinsville, a section of Bridgewater Township. The Middlebrook Encampment site includes part of the ridge of the First Watchung Mountain. Its position provided a natural fortress not only protecting the Continental Army but also overlooking the plains towards New Brunswick, where the British forces were stationed in 1777. A surviving earthen redoubt believed to date to the 1777 encampment is also located on the mountain within Washington Valley Park. The strategic strength of the army's position on the Watchung or Blue Mountain ridge contributed ultimately to the success of the Continental Army by lengthening the war and wearying the British forces during both of the army's stays.

First Middlebrook or the Spring Encampment (1777)

During the winter of 1776–1777, Washington initially encamped the Continental Army at Morristown, New Jersey. After his outpost garrison at Bound Brook was surprised and routed during the Battle of Bound Brook on April 13, 1777, Washington moved the encampment closer to Bound Brook. The army established its Middlebrook encampment on May 28 and stayed there until July 2. A total of 8,298 soldiers were housed in the encampment, but 2,660 of them were sick or disabled, unable to fight. In contrast, the British maintained a force of about 17,000 near New Brunswick, New Jersey. From the heights of the Watchung Mountains, Washington could monitor and counteract British movements. When General Howe decided to move against Philadelphia, concern over the threat by the Continental Army made him choose the safer sea route instead of the faster land route. This led to a significant delay in operations for the British and disrupted plans to reinforce British General Burgoyne in northern New York. On June 30, Howe moved his troops to Staten Island in preparation for his Philadelphia campaign, and two days later Washington left Middlebrook and moved the army to Pompton Plains, New York.

First flag: June 1777

It is largely conceded that it was at the Middlebrook encampment that the first official flag of the United States was unfurled, after a law to adopt a national flag had been passed by Congress on June 14, 1777. This event is commemorated annually since 1889 on July 4 with a changing of the flag, a reading of the Declaration of Independence, and the delivery of an historical address at the Washington Camp Ground. Also, by special order of Congress, a Thirteen Star Flag is flown 24 hours a day at the Washington Camp Ground.

Second Middlebrook or the Middlebrook Cantonment (1778–1779)

Washington used the area around Middlebrook and much of central Somerset County as a cantonment site, known as the Middlebrook Cantonment, during the winter of 1778–1779. He brought about 8,000–10,000 troops to the area between November 30, 1778 and late January, 1779, arriving himself in early December. The main cantonment stretched across a broad swatch of Somerset County including sites in present-day South Bound Brook