The "Official" Story

Everyone knows that Blaxland, Lawson and Wentworth were the first Europeans to succeed in crossing the impenetrable Blue Mountains, and thus opened up the way for the colony to expand onto the vast fertile slopes and plains of the west. Previous expeditions had tried, of course, but all failed. The only way across was via the three explorers' innovative ridge-top route.

Well, it makes a nice story.

The Three sister - Blue Mopuntains