Cross of Burgundy Flag
The saltire design, known as the Cross of Burgundy, was a symbol of Philip I, Duke of Burgundy and father of Charles I, who became Spain's king in 1516. Variants of the Burgundy cross flag- including some versions with smooth-edged saltires- became widely used by the Spanish military on both land and sea. This is the principal flag that flew over Spain's colonial empire in the New World until 1785.
Possibly, Lucas Vázquez de Ayllón brought this flag to Georgia in 1526 when he arrived with 600 Spanish colonists to found the ill-fated settlement of San Miguel de Gualdape. Given the number of Spanish missions, garrisons, and settlements that would follow, this flag almost certainly was used in Georgia.