CHAMPLAIN, N.Y. — Roxham Road is a quiet country road jutting off another quiet country road, where a couple of horses munch on soggy hay and a ditch running along the muddy pavement flows with melted snow. It cuts through a thicket of dormant trees, passing a half-dozen trailer homes and after almost a mile runs into a line of boulders and a rusted railing with a sign: Road Closed.

Chris Crowningshiele has been driving a cab, on and off, for 30 years in this rural corner of upstate New York known as the North Country. He lives south of here in Plattsburgh, and his fares usually come from ferrying students from a state university there or picking shoppers up at a Walmart in his gray minivan. But in recent weeks, riders have been asking him — two, three, sometimes as many as seven times a day — to bring them to the end of Roxham Road.

He is carrying them on the last leg of their journey out of the United States. Just on the other side of that sign is Canada. Border officials and aid workers there say there has been a surge in people illegally crossing from the United States in the months since President Trump was elected, many of them natives of Muslim countries making bids for asylum. Roxham Road, just a brief detour from a major border crossing on Interstate 87, has become one of the busier illegal points of entry.

Mr. Crowningshiele picks up passengers in Plattsburgh, mostly at the airport or the bus station, and over the 25-mile drive north, they have told him that they had traveled from across the country. Some were migrants from Yemen and Turkey. They confided that they were fearful, of what was happening in the countries they wanted to leave behind — not just their homeland but now also the United States — and of what they faced once they stepped out of Mr. Crowningshiele’s cab.