I find it odd that when one has an unobstructed land border, no enemy countries in position to block it, one cannot trade. I don't understand if it's just not working right or a feature. As Great Britain I hold Florida, Georgia, Kentucky and am on very friendly terms with the Iroquois, but can't trade with them. The 13 Colonies are still my protectorate till I take Quebec from the French. I can establish overseas trade with other nations, but not my neighbor.

Does a land-based trade route still have to go through a port?