Monmouthshire, a maritime county of England, having Hereford and Brecknock on the N., Glamorgan on the W., Gloucester on the E., and the Severn estuary on the S. and S.E., and containing over 370,000 acres, most of which is arable, meadow, or pasture land. The surface is varied, being in parts mountainous and rocky, and in others consisting of fruitful slopes and plains, woods, pastures, and well-cultivated land. The Usk, with its tributary the Ebbw, flows through the county, and the Wye and Monmow are on the boundaries. The geological formation W. of the Usk belongs to the South Wales coal-fields, and is bordered by carboniferous limestone, while E. of the Usk lies the old red sandstone. The chief products are iron, coal, limestone, and other stone, the two first being of highest importance, since there are over a hundred collieries, and numerous blast-furnaces, puddling-furnaces, steel and tin-plate works, and rolling mills. A good deal of flannel and coarse cloth is manufactured. The chief headquarters of the coal and iron manufacture are Pontypool, Blaenavon, Tredegar, Rhymney, and Ebbw Vale. The chief towns are Monmouth (capital), Newport (at the mouth of the Usk), Abergavenny, Blaenavon and Tredegar. Monmouthshire was made an English county by Henry VIII. The ruins of Tintern and Llanthony Abbeys are in this county.