Monmouthshire, a maritime county of England, bounded S. by the Bristol channel and the estuary of the Severn; area, 575 sq. m.; pop. in 1871, 195,391. The coast, 22 m. in extent, is exposed to the high spring tides that rush up the Severn from the Bristol channel and sometimes attain an altitude of 60 ft. Vast sea walls and earthworks have been erected. The surface toward the north is mountainous and rocky; adjoining the Severn and the sea is a spacious plain, which the river Usk divides into two parts, called the Wentloog and Caldecot levels. The principal mountains are: Pen-y-Val, or the Sugar Loaf, 1,856 ft. high; Blawrenge mountain, 1,720 ft.; and Skyrryd Vawr, or Holy mountain, 1,498 ft. The chief rivers are the Wye, Usk, and Monnow, the two former of which are famous for their salmon. The soil of the vales and plains is generally fertile. Iron, coal, lead, and building stone are produced. The iron and coal of this county are shipped at Newport. The area of its mineral districts is estimated at 89,000 acres.