Jack Monroe is a fictional superhero appearing in American comic books published by Marvel Comics. The character was originally introduced as the third sidekick under the Bucky identity, initially treated as the original Bucky Barnes before being retconned as a separate character, and later the most well-known incarnation of Nomad.

The character Jack Monroe has a complicated history, and his origin involves a complex series of retcons. Although the character's first real appearance is as "Bucky" in Captain America #153, the origin of the character, first revealed in Captain America #155 (again by Englehart and Buscema), identifies him as the "Bucky" that appeared in Captain America comics which were originally published in the 1950s.

When they were first published between 1953 and 1954 those Captain America stories, which were written by Don Rico and illustrated by Mort Lawrence and John Romita, Sr., starred Steve Rogers (the original Captain America) and Bucky and were clearly set in the 1950s, with the duo prominently battling communism and a communist Red Skull. However, when the character returned in Avengers #4 (March 1964), it is revealed that the original Captain America has been in a state of suspended animation since a battle he fought near the close of World War II, a battle in which the original Bucky perished.

The 1950s stories were thus considered outside of official canon until Englehart's 1972 Captain America storyline, which attempted to resolve the discrepancy by showing how a teenager (Monroe is simply referred to as "Bucky" throughout, the name "Jack Monroe" was introduced in later stories) and an unnamed man (later known as "The Grand Director") had assumed both the public and private identities of the original Captain America and Bucky as part of a government-sponsored program which planned to replace the lost heroes to combat the "red threat". Captain America #155 reveals that the two gained superpowers by injecting themselves with a "Super-Soldier Formula" that they find in old Nazi files. The formula initially grants them abilities similar to those of the original Captain America (Steve Rogers). However, the formula made no mention of the essential Vita-ray exposure portion of the treatment and the absence causes its effects to eventually give them psychotic symptoms, leading to their fight against communism degenerating into random attacks on anyone they deem insufficiently patriotic, including civil rights protesters. As a result, the two are arrested and put into suspended animation by government agents.

This complicated origin is the reason that some sources list Young Men #24 (December 1953; the first appearance of the communist-hunting Captain America and Bucky) as Monroe's first appearance, though the issue was originally intended to depict the original Bucky. A later story, What If #4, (August 1977), further complicates the Bucky history by introducing another "Bucky" (Fred Davis) that takes on the role in 1945, many years before Monroe assumes the title, which makes Monroe the third "Bucky" chronologically.

Monroe was mostly portrayed as essentially having the same powers as the first Captain America, Steve Rogers. This has long been a matter of contention in the comics as Monroe received his powers from the same sample of the Super-Soldier Serum that gave the 1950s Captain America superhuman strength. He became super strong but after being exposed to stabilizing rays (similar to the Vita-rays Steve Rogers received), his strength normalized to peak human.

In Captain America #153–156, "Bucky" and his partner are briefly reawakened decades after being put in suspended animation, but are subdued by Falcon and the original Captain America. In Captain America #232–236 (April–August 1979) — by writers Roger McKenzie, Jim Shooter and Michael Fleisher and artist Sal Buscema — "Captain America" is revived and brainwashed into becoming the fascistic "Grand Director", who shoots and apparently kills his former partner Bucky and later apparently commits suicide. Writer J. M. DeMatteis resurrected the "Bucky" character in Captain America #281 (May 1983), which is the first comic that names him as "Jack Monroe". That story reveals that the gun was loaded with blanks, and the cured Monroe is given the Nomad identity by Steve Rogers in Captain America #282 (June 1983). Nomad then becomes Captain America's partner for the next two years of published comics. DeMatteis' successor as writer of the series, Mark Gruenwald, had Nomad end the partnership in Captain America #309 (September 1985). Gruenwald said he did this "because Nomad made Cap seem old. Cap had to take the mentor relationship with Nomad, and he was coming off as everyone's favorite father figure rather than as the active vital superhero."

However, Gruenwald continued to feature the character in Captain America intermittently. He features in Captain America #324–325 (December 1986–January 1987), and after Steve Rogers is stripped of his Captain America identity, Nomad appears in a storyline which continues for over a year of Captain America stories (#336–350; December 1987–February 1989) where Nomad is one of Rogers's partners as he continues being a superhero under the identity of "The Captain". During this storyline Nomad is depicted as a tetchy and insolent character who takes an instant disliking to Demolition Man, a dislike which only increases when it becomes evident that Vagabond is attracted to him. Though not explicitly stated in the stories themselves, the Captain America letters pages explained that the formula which gave Nomad his powers was again causing him to become aggressive and mentally unstable.