CUMBERLAND MOUNTAINS, the westernmost of the three great divisions of the Appalachian uplift in the United States, composed of many small ranges of mountains (of which Cumberland mountain in eastern Kentucky is one). It extends from Pennsylvania to Alabama, attaining its greatest height (about 4,000ft.) in Virginia. The plateau is rich in a variety of mineral products, of which coal is the most abundant ; beautiful marbles are also quarried in this region. The plateau has an ab rupt descent, almost an escarpment, into the great Appalachian valley on its east, while the west slope is deeply and roughly broken. The whole mass is eroded in Virginia into a maze of ridges. Cumberland mountain parts the waters of the Cumber land and Tennessee rivers. This range and the other ranges about it are perhaps the loveliest portion of the whole plateau. The peaks here and in the Blue Ridge to the east are the highest of the Appalachian system. The Cumberland range is noted for its immense caverns and subterranean streams. Cumberland gap, crossing the ridge at 1,648ft. above sea level, where Kentucky, Virginia, and Tennessee meet, is a gorge about 5oof t. deep. The mountains, river, and gap were all discovered by a party of Vir ginians in 1748, and named in honour of the victor of Culloden, William, duke of Cumberland. Afterwards the gap gained a place in American history as one of the main pathways by which emi grants crossed the mountains to Kentucky and Tennessee. Dur ing the Civil War it was a position of great strategic importance, as it afforded an entrance to eastern and central Tennessee from Kentucky, which was held by the Union arms; and it was re peatedly occupied in alternation by the opposing forces throughout the struggle.