Shiprock is the most prominent landmark in New Mexico.  It is called 'Shiprock' because of a supposed resemblance to an 18th-century clipper ship.  Geologically, it is the eroded remains of an ancient volcano;  what you see is the lava in the throat of the volcano, the cone having eroded away over the eons.

During the time of the westward migrations by wagon train, Shiprock was said to have been an indicator that the wagon train was so-and-so weeks from the Pacific coast.