The Earth Alliance consists of the member states of Earth and the off-world colonies such as Mars and Luna. It was founded in 2085 in the aftermath of WW3.
The Centauri contacted Earth in 2156 which began a rapid expansion in technology and movement throughout the galaxy.
In 2230 the Earth Alliance fought with the League of Non-Aligned Worlds against the Dilgar.
In 2245 contact was made with the Minbari which due to a misunderstanding, led to disaster, and a war which drove the Earth Alliance back home.
After the war, the Babylon project was started, culminating in Babylon 5 in 2257 as common ground for all races of all worlds to meet.
The Shadows had secretly infiltrated the Earth Alliance hierarchy which led to Civil War shortly afterwards.
In 2762 most of Earth's cities were destroyed in another civil war, and Humans mostly survive in colonies on other systems.