Endor was on the outer rim of the Outer Rim- real close to the Unknown Regions. The Ewoks claimed that there were a bunch of other sentient species on the planet, including several that arrived in crashed space ships, but Ewoks were unreliable at best. The Empire found the moon to be an ideal location to build their second Death Star. In order to limit the chances of repeating their previous mistake, with a shield generator protecting the space station from the surface. This led to the Battle of Endor where the shield was single-handedly disabled by Han Solo with no help from anyone. This allowed Lando to destroy the Death Star. The party that followed on the moon was epic in proportions and was voted as the best party of the century by the editors of Dathomir Gentleman's Quarterly.
A bunch of Ewoks: