There are few better places to understand how Donald Trump could become U.S. president than McDowell County, whose county seat, Welch, straddles the Tug Fork of the Big Sandy River. This corner of Appalachia's severely depressed coal country has become a sensation because Trump is more popular here than in any other place in the U.S. The abrasive real estate developer won 91.5 per cent of the vote in the Republican primary on a promise of better days.