There hasn't been a major war between Canada and the United States since the War of 1812. After that war, a treaty was drawn up clearly defining the Canada-US border. But one small island was left out of the negotiations.
The Machias Seal Island is a small piece of land in the Atlantic Ocean. Located near the Gulf of Maine and the Bay of Fundy, the island is pretty much right in between Canada and the United States. The two countries have been fighting over it for 200 years.
Based on the Treaty that defined the border, the US has a claim to the island since it's closer to their border. However, another treaty lays out that the island could be part of Nova Scotia too. Hence the countries have been in a quiet land dispute since the War of 1812. Right now, Canada is winning.
In 1832, Britain who was then in control of Canada, built a lighthouse on Machias Seal Island to lay official claim to it. A lighthouse doesn't actually count as a sovereign settlement though, so the government put two lighthouse keepers living out there to maintain Canada's claim.
To this day, there are always two Canadian lighthouse keepers put on the island to maintain Canada's sovereignty there. Every four weeks, the Coast Guard rotates out the two keepers, who are paid by the Canadian Department of Global Affairs.
The US has not given up, though. They have never accepted Canada's occupation of the island as a sign of ownership. Despite that, they haven't placed anyone there to occupy it either. The real fight though isn't on land but in the water.
Both countries often have fishing boats in the waters surrounding Machias Seal Island, where there is a very lucrative lobster opportunity. Up until recently, this has been a peaceful co-existence.
In June 2018 though, in the midst of Trump's beef with Canada, US border officials stopped a number of Canadian boats and questioned them about illegal immigrants. Canada said they would look into the incident which they say took place in Canadian waters.
Machias Seal Island is only 19 acres in size. The tiny island is home to a Canadian lighthouse, but also a Canadian bird sanctuary since the island has thousands of arctic birds. The Migratory Bird Sanctuary is run by the Government of Canada, who claims the sanctuary is actually located in New Brunswick, again laying claim to the island.
Every year Canadians are also invited to visit the island, with a number of tour companies offering boat rides and sea-kayaking trips and tours there. As for the land dispute, it is still ongoing.
*Cover photo for illustrative purposes only.