They represent direction.
And I’m really not sure what purpose it serve to have Churchill, Canada on the map, but it’s a nice touch.
The Central North American Trade Corridor extends from Alaska and the Port of Churchill in Canada through the Canadian provinces of Manitoba, Saskatchewan, Alberta, and British Columbia, then through North Dakota, South Dakota, Nebraska, Kansas, Oklahoma panhandle, and Texas in the USA and south to Mexico City.
Oh look! They've got a map too! Upper right corner...To Port of Churchill.