Genosha received an entry in the Official Handbook of the Marvel Universe Update '89 #3.
The foundations of Genoshan society has been upset in recent years due to the efforts of outside mutant interests. In the first storyline to feature the nation, some members of the X-Men (Wolverine, Rogue, and their ally Madelyne Pryor) were kidnapped by Genoshan Magistrates, under the order of the Genengineer. Later, in the multi-issue, multi-title X-Tinction Agenda storyline, the X-Men and their allies rescued their teammates, Storm, Meltdown, Rictor and Wolfsbane, from Genoshan brainwashing, toppling the government after discovering their alliance with former X-Factor ally turned mutant hater, Cameron Hodge, and that Havok was one of the Magistrates since having his memory wiped by the Siege Perilous. Havok himself, woken from his conditioning by his brother Cyclops dealt the killing blow to Cameron Hodge in the process. Another ally, a member of the New Mutants named Warlock, was killed by Cameron Hodge. The news of this death was broadcast worldwide.
A different version of X-Factor, including Wolfsbane, later returned to the island to help restore peace between its government and a rogue group of super-powered beings that had fled the island. The Genoshan government was shown with peaceful intentions, even trying to undo the ill effects visited upon Wolfsbane. Genosha was also shown to have typical suburban tract housing, like many small towns in America.
The United Nations ceded the island nation to the powerful mutant Magneto, after he demanded an entire mutants-only nation. Magneto and his Acolytes managed to reestablish a modicum of peace and stability only briefly until civil war broke out between him and the remaining human population on the island led by the Magistrates. Magneto eventually defeated the magistrates and restored order to most of the island, with hold-outs briefly remaining at Carrion Cove before being obliterated.
The elimination of the Legacy Virus gave Magneto a freshly healthy army, leading him to declare a campaign of global conquest. A small team of X-Men stopped this plan, badly injuring Magneto in the process (the original issue presented him as being killed but New X-Men retconned this).
By New X-Men #115, Genosha had a population of sixteen million mutants and a stable, advanced society. However, the entire island was reduced to rubble and its mutant population was slain by Cassandra Nova's Sentinels. There were few survivors, many evacuated, and the Brotherhood of Mutants turned one of the Sentinels into a memorial statue in #132.
A few survivors and newly arriving mutants who wish to help with the rebuilding process remain on the island. Members of this volunteer 'army' include Callisto, Freakshow and Wicked. More are found in the surrounding countryside, some join with Xavier.
In Excalibur #6, some of the captured Magistrates agree with work with Xavier to rebuild the island. Throughout the entire series, Unus the Untouchable and his squadron of mutants remain a problem; they don't wish to be part of Xavier's group.
Later Magneto learned of the Scarlet Witch's nervous break-down and her ever-growing powers to alter reality. Magneto snatched Wanda from her battle with her fellow Avengers and brought her to Genosha, where he asked Xavier to restore the Scarlet Witch’s sanity - but to no avail. The telepath couldn’t help her and, concerned of the threat to reality that Wanda posed, Xavier consulted the Avengers and the X-Men what to do with Magneto’s daughter. Their decision was rendered moot, though, as by the time they reached Genosha reality altered around the heroes - changing into the world ruled by the “House of M”.
While conventional reality was eventually restored, it came at a high price, as thousands if not million of Earth’s mutant population lost their powers or died in the process, leaving only a few hundred mutants alive or powered. Just like most of his new Genoshan allies and enemies, Magneto was among the de-powered people, remaining trapped on the island.
In New Avengers #19-20 it was revealed that energy cannot be created nor destroyed, and the same held true for the energies of the numerous depowered mutants. Eventually, these energies gathered in the form of an unsuspecting energy-absorbing mutant named Michael Pointer. Dubbed “the Collective” by the Avengers, against whom he then fought, the Collective traveled to Genosha and reached out to the startled Magneto. The Collective attempted to restore Magneto’s powers and convince him to lead the remaining mutants into taking over the planet. To the Collective’s surprise, Magneto resisted and allowed the Avengers to separate the energy from his body and send it into the sun. The comatose Magneto is also taken into SHIELD custody, but the helicopter that was supposed to transport him off Genosha explodes once it lifts off. Magneto’s body is not found.
To the date Genosha is now completely dead. Already in ruins before, the battle between the Inhumans and the O*N*E further destroyed the once proud island nation. Since Magneto was the last person on Genosha, it seems that it’s now totally uninhabited.