The 17 market regions start locked, all but the home port's. On the map a locked region is shaded dark, its ports are small faint dots that can't be clicked (zoomed in, their marinas show like any others, and their names are shown dimmed), its land drawings aren't drawn, and the Markets tab leaves its ports out. No route can stop at its ports and no hub can be built there, but ships may sail through it. Port growth messages for its ports aren't logged.
A region's area on the globe: every point belongs to the region of its nearest port.
One more region can be unlocked every 5 company levels. The level-up toast says "a new region to unlock", the World tab gets a black dot, and an "Unlock a region" button (with the count, if more than one) heads the map's top-right panel. It opens the choice: the regions are outlined, every locked region has a button with its name at its middle, the locked region under the mouse (or button) lights up gold, and a banner at the bottom explains (Cancel or Esc closes it). Clicking a region or its button arms it ("Click again to unlock Southeast Asia"); clicking again unlocks it for good, with a log message.
Saved per company (multiplayer: each player's own; joined players' unlocks go through the host).
Maritime Empire