According to this link
http://www.misapellidos.com/ver_datos.phtml?cod=34733Campos is a Castillian last name from
Tierra de Campos (the land of fields (?), a place in the Spanish provinces of
Leon, Valladolid and
Valencia. Apparently, it was initially used by the nobility native to the region. Otherwise, as
Jordan said, campo is the Spanish word for a field, or more loosely, the rural province.