If one of the areas on your map is covered in clouds then you will have to make the map to unlock it.
Here’s a list of where you craft each map:

• Khan Mires Map: Made in Darfoot (Blue Peaks Valley)
• Dragonwing Map: Made in Mirages (Khan Mires)
• Nameless Forest Map: Made in Mirages (Khan Mires)
• Golden Canyon Map: Made in Greenlee (Nameless Forest)
• Emerald Valley Map: Made in Beorn (Golden Canyon)
• Extinct Sea Map: Made in Greenday (Emerald Valley)
• Wolf Heath Map: Made in Aery (Blue Peaks Valley)
• Cold Lands Map: Made in Gold Rush (Golden Canyon)

• Eternal Ice Map: Made in Stoneswick (Cold Lands)

• White Bear Plateau Map: Made in Northridge (Eternal Ice)