United Earth was a planetary state created through the unification of Earth in the 22nd century, following first contact with Vulcans in 2063. United Earth continued to exist as a member world of the United Federation of Planets when Earth helped found that interstellar state in 2161. (Star Trek: First Contact, Star Trek: Enterprise)
By the 2150s, the United Earth government was coterminous with all major settlements made by Humanity. This included all territory on Earth itself, after all previous Human governments united into one organization. United Earth controlled all of the Sol system, but in the 2150s, the organization had begun to spread to other nearby star systems.
Planetary bodies that had major Human settlements or military installations on them in the 2150s included:
In the Sol system:
- Mars – Martian colonies
- Several colonies in the asteroid belt (ENT: "Terra Nova")
- Jupiter Station, a Starfleet support facility in orbit around a gas giant, Jupiter (ENT: "Silent Enemy")
- Titan, used for hazardous environment training by Starfleet (ENT: "Strange New World")
In other solar systems:
- Alpha Centauri – Proxima colony
- Deneva – Deneva colony
- Terra Nova – Terra Nova colony (contact lost in 2083, reestablished in 2151)
- Vega – Vega colony
In the first half of the 22nd century, the most significant Human presence in space beyond the Sol system itself was in the form of "Boomers", independent Human traders that formed a merchant marine using crude, generationally-owned starships that took years to travel between destinations. While nominally under the control of the Earth Cargo Authority, by their very nature, the Boomers were frontiersmen without any real oversight from Earth and generally handled their own affairs. In a sense, these small (with approximately two dozen crewmen on the common Y-class freighter) and mobile ship-borne communities could be seen as "colonies" of a sort. During the second half of the 22nd century, as faster warp drives became more commercially available, travel time between destinations was cut down from years to months or weeks, and response by official United Earth Starfleet ships was, for the first time, made a practical reality; the independent frontier lifestyle of the Boomers gradually came to an end. (ENT: "Fortunate Son")
Even after United Earth was formed, many nation-states and confederations of Earth retained their individual identities. These included the African Confederation, Canada, the European Alliance, Russia, and the United States of America. (TNG: "The Naked Now", "The Price", "Conundrum", "Lower Decks"; VOY: "Imperfection")
United Earth had many agencies. These included an early form of Starfleet (prior to 2161), Military Assault Command Operations (MACO), the United Earth Space Probe Agency, and the United Earth Diplomatic Corps, the latter of which was responsible, among other things, for running the United Earth Embassy on Vulcan during the 22nd century. (ENT: "Broken Bow", "The Expanse", "The Forge"; TOS: "Court Martial")
The term "United Earth" was used in relation to a New United Nations declaration of 2036. (TNG: "Encounter at Farpoint") The phrase was used as a name as early as 2067, for the United Earth Space Probe Agency. (TOS: "Court Martial"; VOY: "Friendship One")
- Minister Nathan Samuels (2155; presided over the talks regarding the Coalition of Planets)
- Councilman Jonathan Archer (2175-2183; represented United Earth to the Federation Council; previously ambassador to the Andorian Empire; later Federation President)
In TNG: "Attached", when Dr. Crusher implies 2150 as the year that the last holdout(s) finally joined a unified government on Earth, she refers to it as "World Government", not United Earth.
According to an unseen It's Federation Day! article created for the Picard family album in Star Trek Generations, Thomas Vanderbilt was the United Earth ambassador to the Federation Founding Ceremony.
The seal of United Earth first appears in ENT: "Home", on a podium Captain Archer speaks at, moments after arriving on Earth, when he and his senior officers are welcomed back after having saved the planet from the Xindi. The idea of devising the United Earth seal and introducing it in "Home" was thought up by the episode's writer, Mike Sussman. He later recalled, "They pitched to me that there was going to be a big ceremony and that there'd be a podium with a Starfleet logo on it. My immediate thought was, 'I don't know if that's right.' They haven't just saved Starfleet, they've saved the planet, so shouldn't that be the equivalent of the flag of our nation and our nation is Earth." (Star Trek: The Official Starships Collection issue 82, p. 15)
While considering how the symbol should look, Mike Sussman also questioned who the governors of Earth in the 22nd century would be. "I found myself asking 'what is the government of Earth like?'" he remembered. "We certainly said in the [ENT] pilot that the nations of Earth were united but what is the name of the government? Was it the new United Nations? Was it the United Earth? We certainly heard both terms thrown about." A passionate fan of Star Trek: The Original Series, Sussman was meanwhile aware that, in the earliest episodes of Star Trek, there are several references to the United Earth Space Probe Agency, as the idea of the Federation hadn't yet been established behind-the-scenes. He also knew that, in TOS second pilot "Where No Man Has Gone Before", there is a styrofoam cup adorned with a symbol that looks like it might represent United Earth. (Star Trek: The Official Starships Collection issue 82, pp. 15-16)
Deciding precisely how the logo in "Home" should look involved much consideration. "For a long time, I was actually dreading designing the United Earth logo," admitted Michael Okuda, "because it was such an important thing." (ENT: "The Forge" audio commentary, ENT Season 4 Blu-ray)
Inspiration came from the aforementioned cup which appears in "Where No Man Has Gone Before" and seems to be decorated with the symbol of United Earth. "It kind of looked like the UN logo, that said USS Enterprise and had palm leaves on it," Mike Sussman remarked. "We clearly weren't going to do that logo exactly but I wanted to see that design." (Star Trek: The Official Starships Collection issue 82, p. 16)
As it turned out, Mike Okuda needn't have worried about the task of designing the seal of United Earth. "When it came time to design," he said, "you suddenly realize, 'Well, you want to point toward the Federation [in design lineage] and you want to show Earth,' so it's actually created very quickly." (ENT: "The Forge" audio commentary, ENT Season 4 Blu-ray)
Mike Sussman was extremely pleased with how the symbol was introduced. "To me, it was [a] very moving and emotional moment where Archer is addressing the people of Earth and there is the Earth logo: Earth embraced in the palm leaves just as the Federation logo is the universe in that same kind of graphic," he observed. "I think that logo alone speaks volumes to me about Star Trek and its ideals and about where we will hopefully go as a species and that is something to [hope] for. To me, it is as hopeful as the image of Earth rising over the moon that the Apollo astronauts photographed." (Star Trek: The Official Starships Collection issue 82, p. 16)
In the novel Articles of the Federation, it is revealed that United Earth came into existence in 2130, with the signing of a document called the Traité d'Unification at the Place de la Concorde in Paris, France; the Place de la Concorde later becomes the site of the Palais de la Concorde, the Federation's capitol building. The novel The Good That Men Do followed the notion that the last nation to become part of United Earth was Australia.
The short story "Eleven Hours Out" in the anthology Tales of the Dominion War indicates that United Earth is a parliamentary system, as an unnamed Prime Minister of United Earth is described as touring the devastated city of San Francisco after the Breen attack of 2375, along with the President of the United States and Federation President (established in a subsequent novel, A Time to Kill, as Min Zife of Bolarus). The novel Starfleet: Year One features a character named Lydia Littlejohn, who served as President of United Earth during the Earth-Romulan War. If the apocryphal stories are accepted as being in continuity with one another, this may be an indication that United Earth utilizes both presidential and prime ministerial offices, akin to the systems of the present-day State of Israel or Italian Republic. (In such systems, the President is usually the head of state, and the Prime Minister is the head of government.)
The Star Trek: Enterprise novel Last Full Measure reveals that United Earth was involved in a number of very low-level conflicts with factions on alien planets (not full governments) and a rebellion on Mars in the years prior to the Xindi attack of 2153; MACO forces played a decisive role in those conflicts. United Earth's military is also revealed to have inherited the martial funeral ceremony of flag folding.