With border running through backyards, residents of US-Canadian town can be detained for turning down wrong street.

Where before two communities on different sides of the US-Canadian border functioned as one, 21st century security concerns have created a divide marked by sensors and cameras.

The centuries-old border community of Derby Line in the United States and Stanstead in Canada still features a public library intentionally built to straddle the two nations’ border, but locals say the two sides are spending less time together.

With the border cutting right through town, residents now have to worry about border patrol agents responding if they cross their backyard fence or turn down the wrong street.

Al Jazeera’s Scott Heidler reports from Derby Line.