Earth

Earth in the Ultima series is similar to its real world counterpart. In the series, it is the native land of a number of noteworthy personages in Britannia, including Lord British, the Avatar, Iolo FitzOwen and  Sir Dupre.

It is also home to Dr. Eliott Archimedes Rafkin and  Dr. Johann Schleimann Spector, both close friends of the Avatar who are uninvolved with Britannia.

History
In the Ultima series, Earth's history is presumed to be near identical to that of the real Earth, with a few notable exceptions.

The Valley of Eodon
At some point early prehistory, a meteor composed of the same substance as the Moonstones and the Orb of the Moons (possibly Blackrock) collided with Earth, creating a valley upon impact which was mystically out of phase with the rest of the reality, rendering it inaccessible to the rest of Earth's populace save through magical means.

In this valley, known as Eodon, an advanced reptilian civilization called the Kotl arose. They managed to harness the energies of the moonstone meteor such as that they were able to develop and sustain a high level of technology, including intricate machinery and intelligent automata. Desirous of a slave class to support their society, the Kotl kidnapped numerous human beings from a variety of ethnic groups in the outside world and brought them to the valley to be their servitors. Due to this intervention, Eodon came to host a unique commingling of species, with humanity sharing its habitat with a mix of fauna from the Jurassic and Cretaceous periods.

Eventually, the Kotl fell into decline after the moonstone responsible for their rise to power was seized by the Myrmidex, an insectoid race developed by Kotl engineers in the hopes of replacing humans with a less autonomous slave populace. After the collapse of the Kotl Empire, the servitor humans redistributed themselves into tribal communities, usually on the basis of shared ethnic identity. Some survivors of the Kotl race, after being driven from their cities, settled in the wilderness among these people, and eventually came to be known as the Sakkhra.

The Avatar, along with Professor Rafkin, and a young journalist named Jimmy Malone, discovered Eodon sometime in the late twentieth century, following an accident during experimentation upon the Avatar's Orb of the Moons. The hero eventually assisted in the eradication of the Myrmidex - then a major threat to most of the tribal groups in the valley - and the destruction of the Eodon moonstone.

It is presumed that this unique valley still exists in Ultima's Earth, and continues to be walled of from external intrusion.

Late 19th Century Expeditions to Mars
In Ultima' history, the 1893 World's Columbian Exposition in Chicago was home to a demonstration by Percival Lowell, a noted astronomer of the age who theorized the existence of canals on the surface of Mars. The exhibition unveiled Lowell's space cannon, with which the visionary scientist hoped to send a manned train-sized capsule to the red planet, using the explosive powers of phlogistonite as a means of propulsion. Due to sabotage by the Russian monk, Grigori Rasputin (who was acting under the influence of the Martian Raxachk), the space cannon launched prematurely. A number of artists, writers, scientists and other luminaries of the era who had been viewing the space capsule were launched to Mars in the process.

Two years later, in 1895, Nikola Tesla launched a rescue mission to the red planet. The Avatar and Dr. Spector joined his crew, after using the Orb of the Moons to open a time gate in Tesla's secret laboratory in the mountains of Colorado, transposing the two adventurers from the twentieth century to the nineteenth.

The rescue operation eventually proved successful, and the humans from both the 1893 and 1895 launched returned to Earth, along with a group of Martians, disguised in humanoid bodies, who were intent on immigrating to Earth after the effectual ruination of their home world.

A public celebration followed the return of the explorers, implying that in Ultima's chronology there was known space travel as early as 1895, although it is unclear as to how much of their journey the returning heroes shared. The reality of Martians among Earth's populace was kept a sworn secret between those who knew of it, fearing prejudice against the extra-planar visitors if they were revealed.

Alterations of Earth's Time Line by Minax
During the events of Ultima II, Earth's history was manipulated by the ministrations of the enchantress Minax, resulting in a significantly altered history. In this changed time line, magic was a concrete part of Earth reality and mankind lived in conflict with orcs, daemons and other fantastical creatures. Hostilities between nations on this alternate Earth escalated such as that most of the populace was destroyed in a nuclear holocaust in 2111 A.D.

Due to the appearance of time doors, however, people of Earth were able to move temporally between four different points in the planet's history. These included the era of approximately 9 million B.C., when the Earth's continents were still locked in Pangea; the year 1423 B.C.; the year 1990 A.D. and 2112 A.D., a year after the nuclear cataclysm. This strange fluidity of time resulted in a past consciousness of the impending future destruction, and a number of survivors of this event unified in creating a council to research the Minax's instrumentality in the Earth's eventual doom and the possibility that history could be altered to avert it. The head of this committee was Lord British.

Likely due to the temporal travel the time doors allowed, Earth's history became even more bizarre, with anachronistic persons and technology moving freely into past or future time zones. Advanced weaponry and transportation became available throughout the four zones effected. Experienced astronauts could be found in the primitive villages of prehistory. Uncharacteristically advanced civilizations emerged in the fifteen century BC. The remnants of the USSR seemingly resettled in the apocalyptic wasteland of 2112, where they maintained a temporal monopoly on space technology.

Eventually, following the death of Minax in the extra-temporal Time of Legends, the time line of Earth returned to its original state, and the cataclysm of 2111 was averted. Memory of this alternate history was gone, save for in the mind of the Stranger who slew Minax, and among a select few (such as Lord British) who arranged for the Stranger's mission.

Ultima II
In Ultima II there were several settlements throughout the various time zones of Earth - most of which likely ceased to exist after the time line was righted.

Pangea
 * Baradin's Town

1423 B.C.
 * Castle Britannia
 * Le Jester
 * Towne Linda

1423 B.C.
 * Castle Britannia
 * New San Antonio
 * Port Bonifice

Aftermath
 * Pirate Harbour

Ultima IX
In Ultima IX, the Avatar begins the game at their house on Earth, where various tutorials instruct the player as to how to interact with the game world. The in game cheats can also be found in this location, over the fence from where the sword practice tutorial takes place.

Trivia

 * In Ultima II, the coordinates for Earth are 6,6,6, a reference to the infamous "number of the Beast" in the Book of Revelations.
 * In Ultima IX, the Avatar's starting point at home on Earth seems incongruous with the ending of ''Ultima VIII, where the hero seems to return to an already conquered Britannia.