The Miramichi River Valley system, in New Brunswick, is comprised of 37 major tributaries containing over 7,700 individual streams most of which have their beginnings in the Miramichi highlands of New Brunswick. This vast stream network provides 5,500 hectares (13,600 acres) of mostly pristine fish habitat and is why the Miramichi is the worlds largest producer of Atlantic salmon. The Miramichi River has a maximum axial length of 250 km and drains an area of approximately 14,000 sq. km. There are two major branches: the Northwest Branch covers about 3,900 sq. km. and the Southwest Branch about 7,700 sq. km. of drainage area. The two branches drain into a common estuary and subsequently drain into the Gulf of St. Lawrence at latitude 47 deg.N.

The Miramichi valley was occupied by glacier ice until about 12,800 years ago. Following this the valley was inundated with marine water until isostatic uplift raised it above sea level between 10,000 and 12,000 years ago. At which time the Southwest Miramichi entrenched itself into the landscape forming its basic configuration. A state of guasi-equilibrium was established in that the river flows in a sinuous channel or channels throughout the year, periodically flooding the broad flat valley floor. The actual course of the channel may change slowly with time, scouring and eroding flood plain deposits as it shifts. Channels are abandoned as sediment aggradation occurred within them by lateral accretion. It would appear that changes in the flood plain and channel were more significant between 1809 and 1930, than subsequent to 1930. The first period marks a time of climatic change and rapid changes to the Miramichi drainage basin.

North American native people first settled the Miramichi several thousand years ago. No doubt drawn here by the abundance of Atlantic salmon, caribou, moose and other game.
Europeans began to settle on the lower section of the Miramichi river system in the early 1600's. In the late 1700's settlement increased dramatically with the demand for pine logs for ship's masts. It was in the late 1700's and the first half of the 1800's that the Main Southwest Miramichi was settled. Since then the area has expanded based on the demand for forest products.

Of secondary importance was the Atlantic salmon and up until the mid 20th century it served as a food staple but its economic value decreased as runs did. Starting in the 19th century, salmon angling gained in popularity on the Miramichi until it reached a multi-million dollar business in the mid to latter part of the 20th century. It is now an integral part of the Miramichi economy and draws people from all over the world to fly fish for Atlantic salmon.

As recently as the mid 1960's salmon runs are estimated to have reached a million fish. Although the runs have since declined, the Miramichi River System is still the largest producer of Atlantic salmon in the world.