As a result of frequent changes in its ownership, the Lombards called the city Campus Vassorum ("Vassals' Territory"), which later became Campobasso.

The principality of Capua, established in 860,[6] included the counties of Venafro, Larino, Trivento, Bojano, Isernia, Campomarino and Termoli.

[8] Following a constitutional amendment in December 1963 the province of Campobasso was detached from Abruzzo, given the status of Region, and renamed Molise.

The situation remained unchanged until 1970 when 52 municipalities were detached to form the province of Isernia, established under Law No.

The terrain is varied extending from the mountainous Apennines, down through hills, lakes and inland rivers to the Adriatic coast.

The central Valle del Biferno includes the 7.45 km2 (2.88 sq mi) Lago di Guardialfiera, to the east of Castelmauro.

[10] As of 1 January 2014, the most populous communes (comuni) in the province are Campobasso (49,392), Termoli (33,478), Bojano (8,125), Campomarino (7,723), Larino (6,910), Montenero di Bisaccia (6,798), Guglionesi (5,422), Riccia (5,332), San Martino in Pensilis (4,827) and Trivento (4,788).

[14][15] The city of Campobasso has several landmarks including Manforte Castle (1450), the cathedral and several old churches including San Bartolomeo, Campomarino, Larino (inhabited since the 5th century BC) and the fortifications of Monte Vairano, Gildone, Duronia and Terravecchia di Sepino, the Roman city of Saepinum, with its forum, basilica, baths and theatre.