Why were American settlers so eager to head west?

There are many reasons as to why settlers gradually began to expand to the west. With ideas like Manifest Destiny (which, so the pioneers thought, was a God-given right to the land), settlers had no moral objections to claiming the land as their own. As to why they wanted to move, the primary reason was to look for a better life.
As the Eastern cities that worked as ports to the sea became crowded, available jobs and farmland became scarce. As a consequence, the west began to be explored; since the land there was widely unsettled, it became a prosperous area for people to begin a new, individual life. The land, having not been industrialized, was largely untouched. The largely competitive nature of the condensed cities often led to financial difficulties, so the opportunity to expand west and "live off the land," so to speak, quickly became popular. Of course, once the great value of the land and its natural resources became known, more and more people began to expand west, and before too long the west, too, became industrialized and heavily populated.