The Gentleman has been active in Astro City since the early 1940s.
In the late 1940s, during a battle with his arch-nemesis, Professor Borzoi, an peculiar incident occurred in which one of the the Professor's most awesomely dangerous inventions, the Belief Ray, brought to life a gorilla from the feature movie, along with the cartoon character Loony Leo.
In a consciousness streamed awareness, somehow derived from his cartoon developed personality, Leo gave the Gentleman assistance during the battle. The Gentleman returned the favor, convincing the people in attendance to believe in Leo as he was starting to fade from existence after Professor Borzoi's Belief Ray was destroyed. Loony Leo hung around as The Gentleman's sidekick for awhile before wandering off into adventures on his own.
Shortly thereafter, the Gentleman seemingly acquired another sidekick, the Young Gentleman. That specific nature of their relationship a mystery that ended at an unknown time, and for unknown reasons.
Through the years, The Gentleman has been an active defender against the ongoing forces of evil and destruction. Some of the more notable incidents include Madame Majestrix's Invasion of the surface world, the Dark Age period related to Black Velvet's madness overpowering the city in early 1977, the Enelsian Invasion attempt to conqueror all of earth, and the Conquistador's Plot of revenge and redemption.
In recent years, he has taken a more active role as a member of Honor Guard. Given his powers, and his impeccable reputation for over seven decades, it is a bit surprising that it took so long for him to be included. Perhaps, like the heroine Winged Victory, he has declined invitations in the past.