As a bastard sword, Longclaw is longer than a longsword, and is typically worn on the back. It once had a bear's head engraved on the pommel, but this was replaced by a stone wolf's head to reflect Jon Snow's Stark heritage.
Longclaw was passed down through House Mormont for about five hundred years. Jeor Mormont passed the sword down to Jorah Mormont when he stepped aside and joined the Night's Watch. When Jorah escaped justice to the Free Cities, he left Longclaw behind and Jeor retook possession of it.
In saving Jeor's life from a wight attack at Castle Black, Jon Snow set a fire that damaged Longclaw's hilt. Jeor had the hilt replaced with one capped by a wolf's head and gave the blade to Jon. Jon noted the appropriateness of a bastard wielding a bastard sword.