The Taurus Reach is a region of space in the rimward Alpha Quadrant. A zone of Federation expansion in the mid-23rd century, the Reach was also bordered by the Klingon Empire and the Tholian Assembly. The Klingons called the area the Gonmog sector, while the Tholians knew it was the Shedai sector. The Taurus Reach was considered strategically valuable by all three galactic powers.
The Taurus Reach was once home to the Shedai, a vast and powerful empire, who ruled the region from their homeworld of Jinoteur IV. The Shedai established outposts on many worlds within the Reach, including Erilon and Ravanar IV. During the height of their empire, the Shedai made genetic alterations to the proto-Tholians, engineering them into a slave caste. (Star Trek: Vanguard novel: Reap the Whirlwind)
After the fall of the Shedai, the Tkon Empire rose, approximately 600,000 years before the 24th century. The Tkon homeworld was along the outer edge of former Shedai holdings. (Star Trek: Vanguard novel: Open Secrets)
The Taurus Reach was partially charted in the early 2260s by the USS Constellation, under the command of Commodore Matthew Decker. The Constellation's crew discovered an unusual metagenome. Seemingly artificial, but with highly advanced properties, the metagenome was soon found to be present on many planets throughout the sector. This discovery prompted Starfleet's intense interest in the region. Soon a massive colonization effort was underway, and Starfleet constructed the massive Starbase 47, nicknamed Vanguard. Ostensibly for support and defense of these settlements, Vanguard's true purpose was to study the metagenome and the ancient technology found in the Reach. (Star Trek: Vanguard novel: Harbinger)
Pacifica was among the worlds in the Taurus Reach colonized by the Federation in the early 2260s. (Star Trek: Vanguard novel: Reap the Whirlwind, Star Trek: Pendragon: "The Significance of a Single Day")
It was eventually discovered that the region had once been controlled by a race known as the Shedai, non-corporeal lifeforms who had genetically manipulated prehistoric Tholians for use as slaves. The Tholians and other subject races rebelled, and the Shedai were driven into hibernation. The Shedai awoke in 2265, and seeking to reclaim their territory, they slaughtered several Federation and Klingon colonies. Starfleet stopped them at their homeworld in the Jinoteur system, causing the Shedai to disperse throughout the Reach. (Star Trek: Vanguard novels: Summon the Thunder, Reap the Whirlwind)
Within a century, Starfleet had further explored the Taurus Reach. By then, the Federation had established a presence near its far side, which included the abortive terraforming attempt on Velara III near the Pleiades Cluster and the Taurus Dark Cloud. (TNG: "Home Soil"; Star Trek: Star Charts)
During his wanderings in the 2350s, Timothy Sinclair explored the Taurus Reach; he later returned in the mid-2370s, and again in 2385. (Star Trek: Pendragon: "Past Watchful Dragons", "Of Shadows and Starlight", "Missing Person", "Another Time, Another Place", "Starkindler")