The legacy of the Flash began in 1940, when college student Jay Garrick breathed in hard water vapors, thus gaining super-speed. Adopting the heroic codename "The Flash", he would go on to become a founder of the legendary Justice Society of America.
His first successor was police scientist Barry Allen, who gained super-speed powers in 1956 after being accidentally exposed to electrified chemicals. Allen used his powers to become the Flash II. Three years later, Allen's accident was duplicated, leading to young Wally West to become Kid Flash.
In 1960, Barry Allen married his long-time sweetheart, Iris West. That same year, the Flash II helped found the Justice League of America.
In 1965, Barry and Iris Allen had a daughter, Carrie Allen.(1) Six years later, in 1971, Wally West became the Flash III. Soon after that, he married his long-time sweetheart, Gail Manners. That same year, Barry and Iris West had a son, Blaze Allen.(2)
In 1973, Wally and Gail West had a daughter, Iris West II. Meanwhile, Barry Allen's influence extended outside of the world of super-heroics. A lecture he delivered in 1974 inspired a young man named Gil Grissom to pursue a career in law enforcement.
Barry and Iris Allen had their second son, Bart Allen, in 1981.(3) Their third son, Peter Allen, was born in 1983.(2) In 1984, police scientist Tanaka Rei gained super-speed powers and became the Flash IV.
Carrie Allen reached adulthood in 1986. She used the super-speed she had inherited from her father to become the Flash V. In 1994, Bart Allen became Kid Flash II, in 1995 Iris West II became the Flash VI and in 1996, Blaze Allen became the Speed Demon and Peter Allen became Mercury III.
In 1997, Lia Nelson used her light-based powers to become the Flash VII. The next year, in 1998, Bart Allen became the Flash VIII. The same year, Barry Allen tutored Bart Drake - son of X-Patroller Bobby "The Iceman" Drake - who became the hero Quick Freeze.(2)
In 2002, Mary Maxwell became the Flash IX. The Flash's legacy was shown to have reached around the world when, in 2008, a young Japanese man became the Well-Spoken Sonic Lightning Flash.
In 2014, Wally West II, first cousin twice removed of the original, became Kid Flash III.
The Flash's legacy reached down through the centuries. In 2645, John Fox became the Flash X. He would later travel to the year 85,625 and join Justice Legion A.
In 2968, Don and Dawn Allen, distant descendants of Barry, became the Tornado Twins. In 2994, Dawn's daughter, Jenni Ognats, joined the Legion of Super-Heroes as XS.
(1)This character is from John Byrne's Generations books.
(2)Based on one of the Amalgam characters.
(3)I know Bart is supposed to be Barry's grandson, but since I am eliminating all of that business of Barry and Iris living in the future, I felt that it simplified things to make him Barry's son.