A map, which was scribed in Mexico on October 30, 1770, and is considered among historians to be the first map showing the San Francisco Bay, will be auctioned off to the highest bidder on October 25.

San Francisco was officially founded on June 29, 1776, when colonists (surprise!) from Spain (surprise, again!) established the "Presidio of San Francisco at the Golden Gate and Mission San Francisco de Asís," both named for Francis of Assisi. Before then, various marine vessels had passed through the San Francisco Bay on explorations; SF was first discovered by Captain Juan Gaspar de Portola on November 4, 1769, on an overland exploration expedition that saw him and his crew climb to the top of Sweeney Ridge —  looking over the SF Bay.

Less than a year later, the first-ever map showing the San Francisco Bay would be drawn into existence. That map will go on auction in late October.

The original manuscript depicting San Francisco was signed and created by Miguel de Costansó, a Catalan cartographer and engineer for the Portola Expedition. (This expedition, per the National Park Service, was the first exploration of what is now California by a European nation; it's also regarded as the beginning of Spain’s colonization of the Golden State.)

The map was scribed in Mexico on October 30, 1770, and is widely the first map to depict the San Francisco Bay.

“The map was created in conjunction with Costansó’s written report of the expedition, published in 1771 as Diario Historico de los viages de mar, y tierra hechos al norte de la California, the first book on California and itself a rarity,” Bonhams, a privately owned international auction house and auctioning party behind the map, said in a statement published by KTLA.

Bonhams — which is one of the world's oldest and largest auctioneers of fine art and antiques — has noted that there are three versions of this map. It was the second example to first depict the SF Bay Area; the third was printed in 1771 using the second manuscript.

How much is the map expected to fetch at auction, you ask? Somewhere between $600K and $800K, though bidding will begin at $500K.

You can view the auction page for what Bonhams is calling "the most important 18th century map of California," here.

Photo: Courtesy of Bonhams