The calculated distance (air line) between Castries and Le Gros-Morne is approximately 49 miles respectively 78 kilometers.
By car or train, the actual journey to Le Gros-Morne is certainly longer, as only the direct route (as the crow flies) between Castries and Le Gros-Morne has been calculated here.
Air line (approximately)
78 kilometers
42 nautical miles