The Earth Alliance has heavily colonized the Sol system as well as a variety of other worlds. By 2259 the Alliance had established more than two dozen outposts and colonies in fourteen different solar systems.Circa sixty of them have been identified in Babylon 5 media so far. 
Home System Colonies
- Luna: Traditionally "the moon". Located there:
- Mars Colony: Earth's first and largest planetary colony, their independence was ratified by EarthGov March 3, 2262.
- Io: One of the moons of Jupiter and the site of Earth's primary Jumpgate.
Minor Colonies and Outposts
- Aris Colony: A remote outpost that was attacked by Raiders during the Shadow War. During the ensuing evacuation Ben was separated from his daughter Alison, though they were eventually reunited on Babylon 5 by Michael Garibaldi.
- Arisia III: The Arisia Mining Colony was a small orbital mining operation over Arisia III, owned and operated by the Cole Mining company. The colony was destroyed by the Shadows in 2259.
- Crenshaw's World: A minor colony. In 2271, fugitive war criminal Alfred Bester had a contact on Crenshaw's World that had been supplying him with his much needed medication, until Michael Garibaldi discovered the link.
- Flinn Colony: During the Earth-Minbari War, ground-based human weapons defending Flinn Colony forced the Minbari to land soldiers on the planet, and massive hand-to-hand combat raged across the planet's surface. In the end every human on the Flinn colony was killed, but the Minbari suffered heavy casualties in the fighting.
- Fortune City: A mining colony located on Cestus noted for its Holopeeps and the only Arterial Blockage restaurant in the galaxy.
- Jericho 3: A space station colony near the border of the Earth Alliance. In 2245, it was the home base of the EAS Prometheus prior to its fateful mission into Minbari space. The colony, and the EAS Euripides, were both destroyed in the very first counterstrike of the Earth-Minbari War.
- MacArthur Midrange Colony: A human colony, established by the Earth Alliance. During the Earth Alliance Civil War, refugees from Sectors 400 through 600 were taken in by the medical colonies at Beta Durani and the MacArthur Midrange Colony.
- Maui colony: A colony with an Earthforce base that was originally settled by Polynesian revivalists.
- New California: Site of a notorious, violent suppression of a workers' strike.
- New Jerusalem: Location of a battle that occurred at some point prior to 2258 and involved Earthforce and Colonel Ari Ben Zayn.
- Omega 7: An Earth Alliance Mining colony. In February 2259, Ensign Matthew Gideon was dropped off on Omega 7 by Galen following the destruction of the EAS Cerberus in the Lanep System. David Williams was working on Omega 7 in 2266 during the Drakh attack on Earth.
- Seti Gamma II: The location of an advanced bioweapons testing center that used to be run by General Thompson. It is also the center of operations for Pro Zeta Corporation.
- Sheffer IV: The larger of the two colonies in the Sheffer System. Known to its inhabitants simply as Aztlan.
- Sinzar: The site of a notable battle of the Earth-Minbari War where Earthforce ships managed to badly damage a Minbari cruiser, which tried to escape. Before it could get away though, a crippled Nova class dreadnought rammed the Minbari ship, destroying them both.
- Sirius IX: A small colony world with little to offer visitors, until the Neural Archives were built in 2540.
- Tariff's Colony: A commercial colony whose economy functions on bribes, bets and payoffs. The colony has a domed ice mining operation on the local moon with an orbiting space station. In 2267 the Excalibur visited the colony to investigate some ancient alien ruins uncovered on the moon.
The Earth Alliance also includes fourteen distinct colonies named 'Beta', stemming from a period during the early colonisation period in the mid-to-late 22nd Century when Ancient Greek symbolism experienced a brief revival. Acting almost as a slang term for "less important colony", the name became so common that it was even odds that any inhabited system with more than a single colony would have a 'Beta Colony' or at least a 'Beta City'. Since it was a trend rather than part of a systematic scheme, the appearance of Beta colonies was not typically associated with an 'Alpha', 'Gamma' or 'Delta'.
The practice was so prevalent at the time that even the Centauri picked up on it and emulated this style of naming convention. At the time the Centauri Republic was still attempting to convince humanity that Earth was a lost Centauri colony and so when the Centauri translated the names of their planets and star systems into English, they used Greek lettering too and since to them there could only be one "Alpha" world (Centauri Prime), many of their colonies ended up being called 'Beta' - such as Centauri Beta I - and this can cause confusion with similarly named Earth colonies. According to the Centauri, Earth was "Beta 9"; however when Human scientists finally gained access to Centauri DNA and discovered the two races were not even remotely related the Centauri claimed their previous assertion stemmed from a clerical error and Earth was in fact "Beta 12" and dropped any further attempts to claim kinship.
- List of Beta Colonies
- Beta Colony: The second largest of two colonies in the Sheffer System which is also the location of a pair of small mining stations in the system's asteroid belt. The larger colony is located on nearby Aztlan (Sheffer IV). In 2253, the colony was the site of a series of serial killings specifically targeting telepaths.
- Beta 7: Location of a notorious prison system run by Major John Clemens during the Earth Alliance Civil War.
- Beta 9: Following the Battle of Proxima III, Commander Sandra Levitt of the EAS Heracles went to Beta 9 for repairs, then withdrew from the field until the end of the civil war. Later during the Earth Alliance Civil War, the EAS Damocles and the EAS Orion were disabled in battle near Beta 9 following their bombing of civilian targets on the Beta 9 colony.
- And Now For a Word
- Dark Genesis - The Birth of the Psi Corps
- Rising Star
- The Exercise of Vital Powers
- By Any Means Necessary
- In the Beginning
- The Gathering
- Racing Mars
- Passing Through Gethsemane
- Conflicts of Interest
- Lines of Communication
- To Dream in the City of Sorrows
- Final Reckoning - The Fate of Bester
- JMS post on CIS - 2/14/1997 7:51:00 AM
- The Illusion of Truth
- In the Beginning (Novelization)
- Dining on Babylon 5
- In the Beginning (named in the novelization)
- Moments of Transition
- By Any Means Necessary
- Eyes (episode)
- The Path of Sorrows
- Summoning Light
- Each Night I Dream of Home
- Genius Loci
- Patterns of the Soul
- Deadly Relations - Bester Ascendant (Page: 213/214)
- Space, Time, and the Incurable Romantic
- Value Judgements
- The Official Guide to Babylon 5 (CD ROM)
- Midnight on the Firing Line
- The Face of the Enemy
- No Compromises
- No Surrender, No Retreat
- Between the Darkness and the Light