Master of the Mojave

 is an achievement in Fallout: New Vegas which is awarded for successfully discovering 125 locations.

This can easily be obtained by choosing the Explorer perk when you reach lvl 20 which shows all locations so simply go out and explore!

You can check how many locations you have discovered simply by looking it up in the 'Stats' tab on your Pip-Boy.

Bugs

 * Sometimes, even if you have found all of the locations on the map, the achievement will not be unlocked. For instance, I found every single location on the map excluding Legate's Fort. I did the quest All or Nothing and found Legate's camp, but the achievement was still locked. I haven't found any ways to fix this.