Amelia Island History Mystery Cache

Here's a hopefully easy little puzzle about some history of Amelia Island. We have a few history puzzles like this back home in Massachusetts, so it was fitting to do something similar down here in Northern Florida too!

North 30° 40.U[V+4][W-2] West 081° 27.X[Y-5][Z-1]

Amelia Island has had the flags of eight nations flown over it since 156U.

Soon after European Settlement in Fernandina Beach and on Amelia island began, James Oglethorpe, the governor of Georgia, ordered Fort Amelia to be built at the mouth of the St. Marys River on the island in 173X.

American naturalist William Bartram visited the island in 177W and noticed several large mounds, which local natives referred to as “Ogeechee mounts.”

The town of Fernandina, about a mile from the present city of Fernandina Beach, was named in honor of King Ferdinand VII on January Z, 1Y11.

The Adams-Onis Treaty, signed on February 2V, 1821 officially transferred Spain's territories in Florida, including Amelia Island, to the United States.

Special thanks to rabbitgeocacher for looking after this cache!

You can validate your puzzle solution with certitude.