This ecoregion forms a 40-km-wide band that runs parallel to the Bay of Fundy and along the United States border to the Saint John River valley. The ecoregion is marked by warm, rainy summers and mild, snowy winters. The mean annual temperature is approximately 5°C. The mean summer temperature is 15°C and the mean winter temperature is -5°C. The mean annual precipitation ranges 1100-1400 mm. The mixedwood forest is predominantly composed of sugar and red maple, white and red spruce, and balsam fir. Warmer and moister sites are occupied by sugar maple and beech, whereas drier sites commonly support eastern white pine. The forest becomes conifer-dominated at lower elevations. Palaeozoic metamorphic, sedimentary, and volcanic rocks are the dominant strata. The region's surface represents the southeast-sloping Appalachian peneplain and can reach elevations above 350 m asl. The terrain decreases in elevation and levels out to the west, where rolling and hummocky stony till plains are predominant. Loamy Humo-Ferric Podzols are the dominant soils. In the western part of the region, significant soil inclusions are Gleysols on poorly drained sites, Fibrisols on flat bogs, and Mesisols on fens. The region provides habitat for moose, black bear, white-tailed deer, red fox, snowshoe hare, porcupine, fisher, coyote, beaver, ruffed grouse, bobcat, and muskrat. Forestry and some agriculture are major land uses. Approximately 7% of the ecoregion is farmland. The major communities include Saint John, Sussex, and St. Stephen. The population of the ecoregion is approximately 150 800.
This ecoregion is part of the Atlantic Maritime ecozone.