For all the attention the country's border with Mexico is getting these days, it's worth noting that there's a far more permeable border to the north. The US border with Canada is the longest in the world, stretching more than 5,500 miles across the continent with just 100 or so checkpoints.

Andreas Rutkauskas knows this border, which spans 13 US states and eight Canadian provinces, better than most. He spent three years photographing it for his series Borderline. His images are less a survey of the border and its checkpoints than an exploration of its most remote corners. "[I wanted] to craft my own vision of this border as a sylvan landscape, standing in juxtaposition to the world’s more heavily contested and fortified borders," he says.

The boundary between the US and Canada was drawn after the Revolutionary War, and no one ever saw the need to erect a fence, let alone a wall. Security was never much of a concern until 9/11. Both countries installed surveillance equipment and thermal imaging cameras, embedded sensors in roads, and deployed drones. The number of US border patrol agents grew from a few hundred to more than 2,000, and travelers needed passports to cross.

Rutkauskas got the idea to travel the border in 2011, when the Foreman Art Gallery invited him to join a show exploring increased border security between Quebec and Vermont. He photographed neighborhoods in the border towns of Standstead, Quebec and Derby Line, Vermont. It inspired him to visit other border areas people didn't often see. "I was trying to capture scenes that went beyond the public's general conception of the Canada-U.S. border," he says.

In 2012, he began lugging his Sinar F1 4X5 camera to what would eventually be more than 200 locations, a journey of some 12,500 miles he made by car. He was living in Montreal at the time, and started with day trips to the border towns of New England. Before long he was venturing ever further west to the Rocky Mountains before crossing the continent to photograph the 1,538-mile-long border between Alaska and Canada.

Rutkauskas meticulously researched each area before he visited, printed maps and plugged waypoints into a GPS unit that he often carried. Upon reaching a site, he’d do a little reconnaissance with a digital DSLR, chose the vantage points he liked, then photograph them with the Sinar.

He was usually alone, though occasionally someone checked in to see what he was up to. His crossing from Hannah, North Dakota (population 15) to Snowflake, Manitoba (2) was quite the to-do, with border agents from both countries chatting with him for nearly an hour. But he breezed through the crossing between Windsor, Ontario, (population 300,000) and Detroit (4 million). Traveling the road to Lake of the Woods, on the border between Manitoba and Minnesota, Rutkauskas came upon a sign directing him to "report via videophone at Jim's Corner (8 miles ahead)." He did so, and found a phone, in a phone booth, with two buttons—one to dial Canada, the other to dial the US. He spoke to an agent, who provided him with a reference number that he was to provide to the authorities if stopped. That said, there is no shortage of surveillance along the border. Closed-circuit TV cameras triggered by sensors in the road record crossings between Quebec and New York, for example.

Beyond the occasional checkpoint, obelisk, or sign marking a crossing, there is little along that vast expanse to suggest an international border. Rukauskas' photos show snow-covered peaks, winding roads and small towns that seem suspended in time. Without a signpost or other cue, you're never sure if you're looking at the US or Canada. "I appreciate how despite our sociopolitical differences, the landscape of Canada and the United States along this boundary is essentially indistinguishable," he says. "The notion of drawing a line arbitrarily on a piece of paper, compared to the real life ramifications of that line is intriguing."