What makes St. Augustine a particularly notable Spanish settlement and is it undisputable?

St. Augustine is the oldest occupied city of the United States. It was found in 1565 by Pedro Menéndez de Avilés. The fort defended the trade route between Spain and its colonies. It would also defend the Spanish-claimed land against invasion.

In 1692 the Queen ordered to build a stronger fort, replacing a wood one with a shell stone one. It was used as a refugee for Loyalists to the Crown during the American revolution, served as a prison during the Indian wars, and was a battle site during the Civil War. And it still stands, so it's pretty much indisputable.