A series of gravity stations at approximately one mile intervals has been established eastward from Pittsburgh extending across the Appalachian Mountains and onto the pre-Cambrian outcrops of the Piedmont. The large folds and faults of the steeply folded region have small or negligible gravity anomalies. This is attributed to a uniform density of the rocks involved which is verified by 'density profiles.'There has been much speculation as to the relation of gravity to tectonics and present geology in the northern Appalachian area. This speculation is reviewed briefly and some relations not previously mentioned are pointed out. The major and more continuous gravity features correspond closely with the trends of Appalachian folding, as shown by a map of gravity contours superposed on the relief map of the northern Appalachian area. However, it seems probable that the source of the primary gravity features is in mass distributions rather deep within the earth's crust, which must have their origin in the tectonic forces which caused the Appalachian uplift but are not superficially evident from the surface geology of the area. Some smaller features may be related to structural or lithologic units indicated by the surface geology.