ca 100,000 BBY

The Columi species develop interstellar space flight and go on to survey a number of neighboring star systems before returning to isolation on Columus.
The New Essential Chronology.
 
The recorded history of the Sith race begins on Korriban.
Star Wars Encyclopedia; Jedi vs. Sith: The Essential Guide to the Force.
 
 
 

ca 50,000 BBY

The Yevethan species, young compared to others in the galaxy, gain sentience on the world of N'Zoth.
Coruscant and the Core Worlds Sourcebook, via Time Tales.
 
 
 

ca 36,453 BBY

The Force is "discovered" on the planet Tython during a gathering of philosophers and scientists.
Galactic Timeline on the Star Wars: The Old Republic website.
 
 
 

ca 30,000 BBY

The Rakatans' Infinite Empire reaches the height of its power. Much of their technology is powered by use of the Force, including the Star Forge, a factory-satellite that can build anything its creators can imagine. It will later be revealed that the Star Forge uses and amplifies the dark side of the Force.
The New Essential Chronology, Star Wars: Knights of the Old Republic website.
 
 
A meteor impact on the planet Alderaan wipes out the Killik race. Centuries later, a lake will form in the impact crater. The capitol city of Aldera will be built on that lake.
The Illustrated Star Wars Universe, via Time Tales.
 
 
The first droids are invented in future Republic space.
The New Essential Guide to Droids.