The Map of the Golden Weapons is a map of Ninjago created by Master Wu detailing the exact locations where he hid the Golden Weapons. For fear that he might one day pass, Wu entrusted the care of the map to an honest man.
Way of the Ninja (Flashback)
Shortly after Garmadon was banished to the Underworld, Wu hid the four Golden Weapons of Spinjitzu. Fearing he might die before the weapons were found again, he created a map detailing their locations and entrusted it to Ray. Ray hid it behind the sign of his blacksmith and it remained there in secret for several years.
Samukai's forces eventually learned of the map and launched an attack on the blacksmith shop in an effort to retrieve it. Nuckal and Kruncha infiltrated the building and whilst fighting amongst themselves, managed to locate the map and claim it.
Samukai used the map to locate the Scythe of Quakes, hidden in the Caves of Despair. Despite often consulting it during the mining operations, the Skulkin leader was unaware that it was upside down and thus they were digging in the wrong area. The Map was eventually stolen by the Ninja, who discovered the Skulkin General's mistake and located the Golden Weapon.
It is unknown what happened to it afterwards. It's presumably put back at the blacksmith shop.