[5] Although competitive, the regional rivalry between the A's and Giants is considered a friendly one with mostly mutual companionship between the fans, as opposed to Cubs–White Sox, or Mets–Yankees games where animosity runs high, though sections of each fanbase does harbor towards the entirety of the other.

Originally, the term described a series of exhibition games played between the two clubs after the conclusion of spring training, immediately prior to the start of the regular season.

This series was interrupted minutes before Game 3 on October 17, 1989, when an earthquake, measuring 6.9 on the Richter Scale, struck the San Francisco Bay Area.

As a result, traffic on the roads below collapsed portions of the Bay Bridge and Cypress Street Viaduct portion of Interstate 880 in Oakland (while this disaster killed one person on the Bay Bridge and 42 people on the viaduct, local officials initially assumed that the death toll would be well into the hundreds) was significantly lighter than it would normally be at rush hour.

Former MLB commissioner Bud Selig, who was fraternity brothers with A's managing partner Lew Wolff at the University of Wisconsin, stated that the A's would not be able to survive as a franchise if they remained at the Oakland Coliseum.

The Giants claimed that the territorial rights were "explicitly reaffirmed by Major League Baseball on four separate occasions," when former managing partner Peter Magowan bought the team in the early 1990s.

The Giants stated "upon purchasing the team 20 years ago, our plan to revive the franchise relied heavily on targeting and solidifying our fan base in the largest and fastest growing county within our territory.

Based on these Constitutionally-recognized territorial rights, the Giants invested hundreds of millions of dollars to save and stabilize the team for the Bay Area, built Oracle Park privately and has operated the franchise so that it can compete at the highest levels.

During the final Bay Bridge Series game, Giants and Athletics players both made emotional speeches and took souvenirs from the Oakland Coliseum.