New Sydney was the primary inhabited planet in the Sappora planetary system. It was an independent planet where Starfleet had no jurisdiction. It was also the birthplace of Ezri Tigan. (DS9: "Honor Among Thieves", "Prodigal Daughter", "Field of Fire")
The planet had its own law enforcement agency, the New Sydney police, who's control extended to the other planets in the system. Lieutenant Fuchida was one such police officer who worked for it. The planet also suffered problems with pollution – Miles O'Brien, while investigating a murder on the planet, remarked that a body found in a river had been partially decomposed by organic solvents in the river.
By the 2370s, the Orion Syndicate had begun to establish itself on the planet, represented by Thadial Bokar. However, Syndicate member Liam Bilby considered New Sydney a safer home for his wife and children than Farius Prime. (DS9: "Honor Among Thieves", "Prodigal Daughter")
Due to the vast mining in the system, New Sydney was inhabited and visited by a large variety of species, including Farians, Humans, Trill, Ferengi, and Nausicaans. Lieutenant junior grade Ezri Dax traveled to Sappora VII to use her mother Yanas Tigan's influence with the New Sydney police to help locate Chief Miles O'Brien, who went missing on New Sydney in 2375. (DS9: "Prodigal Daughter")