sentences:  The war also saw the construction of a number of airfields as part of the Northwest Staging Route.However, the influx of southern highway construction crews had a devastating effect on some First Nations, who suffered from a large number of deaths from diseases to which they had no immunity.Other highways were built during the 1950s and 1960s, resulting the decline and disappearance of the riverboats that had provided the main means of transportation until the 1960s.