Along the U.S.-Canada border, an invisible but hardening wall rises

STANSTEAD, Quebec — For some folks living in a cluster of small towns straddling the U.S.-Canada border here, life could not feel more comfortably secure.

Six Canadian and U.S. checkpoints service the 2½ -mile stretch that cuts through the villages of Derby Line and Beebe Plain in Vermont and the town of Stanstead in Quebec. Street cameras, satellite and sensor surveillance, vehicle patrols and the occasional thumping helicopter overhead ensure that residents can’t budge without someone watching.