WordNet (r) 3.0 (2006):

back country
    n 1: a remote and undeveloped area [syn: backwoods, back
         country, boondocks, hinterland]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "back country":
   Lebensraum, air space, back, back of beyond, backwood, backwoods,
   backwoodsy, boondock, boondocks, borderland, brush, bush country,
   bushveld, clear space, clearance, clearing, desert,
   distant prospect, empty view, forests, frontier, glade, hinterland,
   living space, open country, open space, outback, outpost, plain,
   prairie, steppe, sylvan, terrain, territory, the bush, timbers,
   uninhabited region, up-country, virgin, virgin land,
   virgin territory, waste, wasteland, wide-open spaces, wild,
   wild West, wilderness, wilds, woodland, woodlands, woods