The name used for the lands of the king around Edoras, including Harrowdale. Here, a Marshal of the Mark was the chief military commander. Typically the First Marshal of the Mark commanded the Riders of the Muster of Rohan in and around the Kings Lands. In the days of Théoden there was no First Marshal of the Mark because he had taken the kingship rather young, and he was able to lead the Muster of Rohan himself.
Encyclopedia entry originally written by Nienna-of-the-Valar