History of Wigan   (Help with ancient and recent history.)

Campfire, the same coal is under Wigan that is under anywhere else in the region. However, it's a long way down. Much deeper than it is anywhere else. That's why it was uneconomical to go for it.
Pits that were 'in Wigan', went for coal under Pemberton, Ince or Haigh. No productive colliery took coal from 'under Wigan'.
Coal was brought 'into Wigan' for use in the mills and engineering, not taken out of Wigan for use elsewhere.