The location of Eastwatch on the continent of Westeros.
Eastwatch, or Eastwatch-by-the-Sea, is a castle and port located at the far eastern end of the Wall, where the Wall drops into an inlet of the Shivering Sea called the Bay of Seals. Eastwatch serves as the main port for the Night's Watch, as the capital city of King's Landing, as well as the cities of White Harbor and Gulltown, are also located on the eastern coast of the continent.
At the time of the series, Eastwatch is commanded by Cotter Pyke.
Season 1
Lord Commander Jeor Mormont tells Jon Snow that four of Cotter Pyke's men found four wights in the snow near Eastwatch. Unlike the men at Castle Black, they had the sense to burn them.[1]
Season 2
Tyrion Lannister takes tremendous pleasure in dumping Janos Slynt onto a boat headed for Eastwatch-by-the-Sea.[2]
In the books
Eastwatch-by-the-Sea serves as the main resupply post for the Night's Watch, with ships stopping there from King's Landing, the Free Cities far to the south, the island of Ibben, and even some Wildling fisherfolk who are permitted to trade there. There is also some clandestine smuggling going on there, which is tolerated only as far as in that it helps the Watch. The Night's Watch possesses a small "fleet" of ships at Eastwatch, but they are not frequently used and thus often left unmanned at tied up at anchor.
Naming
In the novels, the castle is named Eastwatch-by-the-Sea almost constantly. In the TV series, it is called "Eastwatch" the one time it is mentioned in dialogue in the first season, as well as on the map on the HBO website. However, in the second season it was also called "Eastwatch-by-the-Sea" on-screen, indicating that the two terms are interchangeable.