And until Quebec introduced government health care and a highway provided a quick link to Canadian hospitals, most people in Stanstead were born in Vermont. That has left much of the town’s middle-aged or older population, including three of Mr. Yates’s four children, dual citizens.

Even those opposed to blocking the three streets with planters or gates agree that it would have little practical effect on residents of either town. There are three official crossings between Stanstead and the United States staffed with border officials from both countries. In recent years, local residents have learned that not reporting to one of them after using an unguarded crossing can prompt a swift and sometimes unpleasant visit from the police or border officials.

Unguarded crossings, like one on Church Street, are monitored by security cameras perched atop light poles. Recently painted marks to guide coming construction work suggest that vehicle sensors lie under the pavement.

But after looking at Stanstead, the Integrated Border Enforcement Team for the region, a group of Canadian and American law enforcement and border agencies, concluded that the equivalent of an invisible dog fence was not sufficient.

“The main problem is illegal immigrants,” said Cpl. Elaine Lavergne of the Royal Canadian Mounted Police, who was among the officials at an open meeting at the Haskell Library in June. She acknowledged that the 100 or so people who attended did not warm to the idea of blocking the streets.

“Of course they were vocal and concerned about what we want,” Corporal Lavergne said from her office in Montreal. “They’re proud of their history. But because of what happened on Sept. 11, 2001, we cannot do nothing. We have to react when there’s a threat.”