There have been a number of characters to take the mantle of the Flash. The first, Jay Garrick appeared in Flash Comics #1 published in 1940. The character is notable for being the first speedster in comics and one of the first to have a singular super-power as opposed to the multi-talented Superman. College student Jay Garrick was working in his lab with an experimental form of heavy water when an accident released the fumes and rendered the young scientist unconscious. He awoke to discover that he could move at superhuman speeds thanks to inhaling the fumes throughout the night. He became a crimefighter battling various villains. The character was also a charter member of the first superhero team, the Justice Society of America. His title was cancelled in 1949 with the publication of issue #104.
Writer Gardner Fox creator of the Jay Garrick Flash introduced a new character in the pages of Showcase #4 published in 1956. The new Flash was police scientist Barry Allen who gained his superspeed when a bolt of lightning threw him into a rack of chemicals. Inspired by the comic book exploits of Jay Garrick he decided to adopt a costume and fight crime as the Flash. The debut of the Barry Allen Flash is populary acknowledged as the starting point of the Silver Age of comics when superheros grew in popularity and sale figures skyrocketed. After a number of trial runs in the anthology title Showcase the Flash was given his own title continuing its numbering from Flash Comics with #105. This character was made a charter member of the Justice League of America.
The current Flash is Wally West, who was introduced in the pages of Flash #110 published in 1959. He was the nephew of Barry Allen's love interest Iris West who gained his own superpowers in an accident identical to that which Barry Allen suffered. He adopted the guise of Kid Flash and accompanied his uncle as a junior sidekick and as a member of the superhero team known as the Teen Titans. He graduated into the role of the Flash after the death of Barry Allen in 1986 and a new Flash series was begun in 1987. The third Flash is a member of the Justice League.
The Flash has appeared on television, most notably in a short lived CBS series during 1990 where he was portrayed by actor John Wesley Shipp aided by special effects and a molded costume. His most famous opponent in the series was The Trickster played by Mark Hamill who parlayed this successful role into in a new career as an animation voice actor.