Double landlocked

From The Volokh Conspiracy

Let’s call a country “landlocked” if it doesn’t border any ocean or sea, except the purely inland seas that have no substantial natural connection to the ocean (e.g., the Caspian Sea or the Aral Sea). This is more or less the standard definition: Paraguay, for instance, is landlocked; Turkey is not. Which countries in the world are double-landlocked, which means that all the countries that they border are themselves landlocked?

What is the northernmost national capital? What is the southernmost national capital? What is the westernmost national capital in the Americas?

Answers here.