I can't wait to see this when it gets a bit of detail on the buildings.
Are you going to go with realism or symbolic? The color of the roads are a bit much right now.
A pilot is the guy who guides ships into harbors. He knows all the dangers in the harbor and where you should dock and so on. Very important man.
Since he has to board each ship, there's usually a pilot station somewhere far out where he can go out in a small boat to meet the ships.
It could also be a coast guard and customs station out there on the islands.
Some cities had immigration and quarantain facilities on islands too, Ellis island in NY for example.