With the first settlement established sometime around 1727 to 1806, during events surrounding the Louisiana Purchase, Keystone began to grow rapidly after the Civil War (1861-1865), attracting farmers and becoming a common starting point for those who were moving to the West from Missouri.
After the completion of the Transcontinental Railroad (1869), Keystone became an important depot; attracting the livestock and meat-packing industries on top of the iron, steel forging, automobile and coal mining industries that were already invested in the city.
In the 1940's, Keystone became the home of the Mystery Man known as the Flash (Jay Garrick); who fought to defend the city against such villains as the Fiddler, the Thinker, Shade, and Turtle. During World War II, the city retooled its industries for the war effort, manufacturing aircraft and supplies for the war waged against the Axis.
In the decades after Jay Garrick’s retirement nearing the ending years of the Cold War, much of Keystone’s business and industry moved across the river to Central City; with many stockyards closing by the 1950's.
Taking advantage of the hero's absence, the Fiddler, Thinker and Shade successfully locked the city within a time bubble and shifted it out of phase with the rest of the planet. As a result, the city disappeared from history and reality; with no one on Earth even remembering that a city had once existed until, around thirty years later, the Flash (Barry Allen) discovered the city after becoming curious over the presence of the Keystone-Central bridge; which up till then only led to empty grassland.
After defeating the three villains and placing the city back into phase with the rest of the world, the city quickly updated itself with modern times, revitalizing many of its old warehouses into fashionable retail destinations while focusing on being a center of industry; home to aircraft and automobile manufacturers, to link with Central City's commercial growth.
After surviving various attacks in New York city, Wally West moved to Keystone City in an attempt to escape.
Neighbourhoods that have been abandoned stretch for miles. Gorilla Grodd attempted to create an army out of the city's animal population only to be thwarted by Flash, Vixen, Pied Piper and Rex the Wonderdog.
Slowly aging to death due to being infected with the drug Velocity-9, Vandal Savage released a massive shipment of drugs into the city to kill off the city's addicts and to entice Wally West into one last battle of the "Flash versus Vandal Savage".
The criminal cartel known as "The Combine" began forming within the city at the same time as Barry Allen returns from the grave. However, when Barry goes rogue and reveals himself to actually be Eobard Thawn (Professor Zoom); destroying the Flash Museum in Central City while fighting Green Lantern (Hal Jordan), Wally West, Flash (Jay Garrick), Max Mercury and Johnny Quick (Jonathan Chambers) unite to defeat him and send him back to his time period.
The development firm known as the Valentine Group developed new recreation centres and malls in Keystone City but soon ran into internal strife when one of its board members sought to blackmail the others by hiring a mercenary to destroy their developments. Wally West's attempts to stop the mercenary (named "Razor") but a civilian is maimed during the fight and Abra Kadabra uses the incident to turn public opinion against the hero by having the victim sue the Flash for negligence. Not used to failing to save people (due to his speed usually enabling him to "do everything") Wally goes overboard and runs himself to exhaustion and is eventually driven into attacking the lawyer prosecuting him in court; resulting in the city banning his presence. Undeterred, while being pursued by police, Wally tracks down Abra Kadabra and manages to reveal the entire conspiracy and enabling the city-wide ban to be lifted, although his reputation had still been tarnished in the public's eye.
During Abra's conspirational attack, following the attempted invasion by the Bloodlines Parasites, the New Blood "Argus" inserted himself into the Keystone City Mob to fight crime within the city. After a brief bout of mistrust, Wally accepted the vigilante's presence within his home town.
Expanding their operations to the United States, Kobra began operating in Keystone City, building a headquarters on the site of an old textile factor by the river, disguising the new building with a hologram. Building a hydro-electric plant under the river, a solar energy plant in a greenhouse, and a wind power plant in a fake cornfield, Kobra began orchestrating the disappearance of many fringe cults in the city and inadvertently gained the attention of Linda Park, which aroused the attention of the Flash.
After the power plants were destroyed, Kobra enacted "Project Morpheus" and enclosed the city within a giant force-field; intending to agitate the major fault lines below the city and use a geothermal tap to power its forces to invade the country. While the city was enclosed and the earthquake triggered, Wally entered the Speed Force while defending Linda and returned with enough power to destroy Kobra's machines and stop their invasion.
After the demon Neron resurrected Abra Kadabra and Doctor Polaris, Abra, using knowledge gleaned from the The Life Story of The Flash biography that belonged to Eobard Thawn, formed an alliance with Polaris and the fourth Chillblaine to create an Ice Age that the biography predicted would destroy humankind. While they managed to create a glacier that broke the nearby dam and travelled into the city, Wally West and John Fox captured Kadabra and forced Polaris to save the city.
However, the city fell into an Ice Age immediately soon after when the sun was engulfed by a Sun Eater; only thawing after Parallax (Hal Jordan) sacrificed himself to restart the sun without causing a supernova.
Chafing over the cost that the Flash's numerous ordeals take on the city's structural budget, Mayor Kingsley forces the hero to operate elsewhere, with Santa Marta, California, eagerly taking him in as their local hero until the return of the Rogues; a scheme concocted by Neron in an attempt to gain control of Wally and Linda's love, forced the city to lift the restraining order that prevented Wally's return.
When Wally disappeared following the Cobalt Blue attack and resulting "Chain Lightning" incident that saw the Flashes travel through time, an alternate Wally; Walter West, arrived in his absence and began operating in Central City; leaving Keystone City to Jay Garrick, until Wally's return.
The city was magically abducted and removed from existence once again, this time by Brother Grimm; who sought everything Wally West had as vengeance for a perceived betrayal from their past.
After Wally brings the city back, Cicada (David Hersch) attempts a religious uprising in Flash's name by assassinating various people associated with the hero; including people in City Hall.
Some time later determined to take over both Keystone and Central cities to spite her ex-husband, Blacksmith (Amunet Black), head of the underground black market the "Network", creates a new iteration of the Rogues and leads them in a campaign to weaken the Flash by targeting his allies. She has Pied Piper framed for murder; Cyborg (Victor Stone) and the Keystone police trapped in the Mirror World; Jesse Quick and Jay Garrick distracted and drawn away from the cities; and has a mirror shield broadcast around the cities so no outsiders could intervene. However, as she leads her team in attacking the Flash she is interrupted by the Thinker, who had taken over Keystone in a bid to acquire the Flash to expand his power.
As the Flash and Cyborg defeat the Thinker, Blacksmith and her "Rogues Army" begin to plunder the cities but are stopped by Goldface (Keith Kenyon) and Union 242, who leads the people of both cities against the villains. While the resulting battle is successful, the Van Buren "Keystone-Central" Bridge is destroyed; but quickly rebuilt by the Flash.
After Hunter Zolomon became the speedster known as "Zoom" and attacked Linda Park-West and caused her to miscarry in a misguided attempt to make Wally West "a better hero through tragedy", Wally made a deal with the Spectre (Hal Jordan) to wipe all knowledge of who the Flash was. As the Spectre's magic even affected him, it was not until Batman (Bruce Wayne) deduced who the Flash was that Wally West recalled his abilities and the Flash returned.
Following the revelation of the Justice League's use of mind wiping against non-redeemable villains, and the "Rogue War" in Central City between the original Rogues and the "reformed" Rogues (which resulted in a final battle against Zoom and Professor Zoom that rewrote history and restored Linda's pregnancy), Wally West and his family was thought to have become trapped within the Speed Force after attempting to drag Superboy-Prime into the ethereal dimension but had luckily been diverted to the planet Savoth, instead.
Over one year later, Wally and his family returned to Keystone City and prevented an invasion from aquatic extra-dimensional beings who intended to dehydrate the planet as vengeance against the Flash dynasty's prevention of their invasion of Savoth.
Following the Flashpoint incident, this version of Keystone City was erased from existence.