The Lost colony of Roanoke was made by England to stop Spanish treasure ships to deliver resources back to Spain.
The problem was that the Spanish knew about the Colony, so they were trying to raid it for a long time, but they always failed.
The Colony would write CRO on a tree to say that they are moving inland for better resources, but if they had a cross it meant they were in danger, but they did not put the cross on the CRO.