[3] When the geyser was given this name in 1870, the top edges of the structure resembled the typical profile associated with the modern concept of a castle, having the appearance of a large keep, multiple turrets, and especially because of the crenellation along the top edges of what resembled its towers.

Over time the cone's shape changes because of the layers of mineral deposited in successive eruptions.

[4] Nathaniel P. Langford gave this account in his 1871 Scribner's article: "The Castle," situated on the summit of an incrusted mound, has a turreted crater through which a large volume of water is expelled at intervals of two or three hours to the height of 50 feet (15 m), from a discharging orifice about three feet (0.91 m) in diameter.

The architectural features of the silicious sinter surrounding it, which is very massive and compact, indicating that at some former period the flow of water must have been much greater than at present, suggested its name.

A 3-D laser scan made of the cone reveals evidence that this geyser has evolved through four to five distinct stages to reach its current configuration.