Based on an article by City Historian Juan Manuel Gomez Encarnación.
Our beautiful Banderas Bay (Bahía de Banderas: Bay of Flags) shares beaches with three municipalities: Cabo Corrientes and Puerto Vallarta in the Jalisco state; and Bahia de Banderas in Nayarit state.
The Sierras (mountain ranges) that surround the bay are Sierra Vallejo on the northern part, Sierra Cuale to the East and Sierra El Tuito to the south and southeast.
It is geographically located between the parallels 20°15′ and 20°47′ N and between the meridians 105°15′ and 105°42′ W.
The bay starts off in the north with Punta de Mita, Nayarit and ends on the south side at Cabo Corrientes, Jalisco.
Its coastline, 65 miles long, is divided in the following: the north coast of Punta de Mita to Bucerias is about 15 miles; East Coast, Bucerintos to Boca de Tomatlán is about 24 miles and the south coast from the west side of the river at Boca de Tomatlán to Cabo Corrientes, approximately 32 miles.
So as you can see, it currently is a bay that is shared by two separate states, Nayarit north of the Ameca River, and south of the river it is part of the state of Jalisco.
The total calculated area of the bay is 381 square miles (Saline and Bourillón, 1988). Its maximum depth is 4711ft (1436 meters) in the oceanic trench located in front of the beaches of Quimixto and Yelapa.
Geologists believe that the bay is the original point where the southern part of Baja California was attached to the continent before it was separated from the North American plate millions of years ago to form the current Gulf of California (Sea of Cortez or Vermillion Sea).
Its name derives from the time of the Spanish Conquest in which Cortés took possession of lands on behalf of the King of Spain, it was noted by his scribes that the local Indians came out to defend their lands with a multitude of flags and they, the Spaniards, won the battle under the Flag of the Blessed Virgin and Santa Cruz (Blessed Cross).
The bay area is very important for the local and Mexican tourism industry, with millions of visitors a year, although the original Puerto Vallarta town and the harbor area have been important for more than a century and a half.
The bay is also well known as a vital area for humpback whale (Megaptera novaeangliae) breeding and birth.