In the centre of todays image is the Peace Arch, which was built in 1921 as a symbol of the peace that has existed between Canada the United States since the end of the war of 1812 (following the treaty of Ghent in 1814), and is located at the Highway 99 / Interstate 5 border crossing between British Columbia and Washington State. There is an inscription on each side of the border, "Brothers Dwelling Together In Unity", on the Canadian Side, and "Children Of A Common Mother", on the American side. Interestingly enough, the Douglas border crossing is the busiest crossing west of the Detroit/Windsor crossing.
Enough history though, on to the image itself! This image shows the stark contrast between the lineup into Canada, verses into the US on a weekday evening. In my mind this image shows two things, first Canadians visit the US far more than Americans visit Canada, since the lineup is exactly the opposite during the day. Secondly it displays how interesting a photo with contrasting areas of focus can be. On one hand you have the empty lanes heading south, leading through the lower front and rear third of the image, while on the other side you have a road full of cars and trucks.