Northern Valley was a region of New Jersey, as mentioned in a Dixon Hill series novel. In the novel, this valley was said to be located in a county, and was populated by bedroom communities and small farms. A major feature of the valley was the Palisades. On top of, and on the western slope, there were the residences of the wealthy. A railroad lane passed through this valley. The valley had one newspaper.
In the Northern Valley, neighbors knew each other by their first names, and would work together to put down brush fires caused by long dry spells. Elms and willows were the dominant trees in this valley.
Detective John Tierney had set up residence in this valley. Licensed as a criminal investigator by the state, he investigated neighborly disputes and petty criminal burglaries by outsiders of the Palisades residences. During his time in the valley, Tierney purchased for himself a dog. (TNG: "The Big Goodbye")