Matchaponix Brook is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the South River

South River (Raritan River)

The South River is a tributary of the Raritan River in central New Jersey in the United States.The South River, formed by the confluence of Matchaponix Brook and Manalapan Brook, becomes tidal downstream of the Duhernal Lake dam and joins the Raritan River approximately midway between New Brunswick...

 (Raritan River tributary) in central New Jersey

New Jersey

New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

.

Matchaponix Brook (Lenape

Lenape language

The Delaware languages, also known as the Lenape languages, are Munsee and Unami, two closely related languages of the Eastern Algonquian subgroup of the Algonquian language family...

 for "country of poor bread") is born in Englishtown

Englishtown, New Jersey

Englishtown is a borough in Monmouth County, New Jersey, United States. As of the 2010 United States Census, the borough population was 1,847....

 at the convergence of Weamaconk Creek and McGellairds Brook, adjacent to the headwaters of Manalapan Brook

Manalapan Brook

Manalapan Brook is a moderately large tributary of the South River in central New Jersey in the United States. It drains an area in both Monmouth and Middlesex counties.-Course:...

. It meets Pine Brook at the county line. Upon entering Middlesex County

Middlesex County, New Jersey

-Demographics:As of the census of 2000, there were 750,162 people, 265,815 households, and 190,855 families residing in the county. The population density was 2,422 people per square mile . There were 273,637 housing units at an average density of 884 per square mile...

, it forms the boundary between Old Bridge

Old Bridge Township, New Jersey

Old Bridge Township is a Township in Middlesex County, New Jersey, United States. As of the 2000 United States Census, the township had a total population of 60,456...

 and Monroe Townships

Monroe Township, Middlesex County, New Jersey

Monroe Township is a Township in Middlesex County, New Jersey, United States. As of the United States 2000 Census, the township population was 27,999. Monroe was incorporated as a township by an Act of the New Jersey Legislature on April 9, 1838, from portions of South Amboy Township, based on the...

. Cutting west and then turning north again, it sweeps around the Old Bridge Airport and meets Barclay Brook just south of the hamlet of Texas. From thence it continues north to meet Manalapan Brook and form the South River.