Church records put the first permanent residents on Jussarö in 1774, and by the mid-1780s six families were living out here, in the outer belt of the Raseborg archipelago where the islands thin to bare rock and open sea. It is a hard place to be casual about. The surrounding water is shallow and reef-strewn, which is why the island would later be given two lighthouses in thirty years. Around 1817 a cavalry officer poked at ore on the nearby islet of Lerharun on a small scale, an early hint of what the rock underneath was hiding.

Once the mine was running properly, life on Jussarö was organised around the shift. Workers were given potato plots and fishing rights alongside modest wages, and the diligent were rewarded with tobacco and spirits — the incentives of a system that could not pay much and knew it. In the earliest years the crew numbered only fourteen to eighteen men, with a pause between 1838 and 1839 before work resumed in 1840. Once permanent housing went up the mine could run year-round: ninety-five men through the summer, about half that through the winter, twelve hours to a working day. The Crimean War shut everything down between 1854 and 1856. Operations restarted afterwards, again with convict labour, now watched by Russian troops, and continued until 1861, when the crown finally gave up on the seam.

The reefs still needed marking. A lighthouse went up on the southern tip of Jussarö in 1891 — a white brick tower seventeen and a half metres tall, banded with red — but it developed structural and technical problems and had to be superseded. Its replacement, lit on 20 November 1922, stands twenty-five metres high on the uninhabited skerry of Sundharu just south of the island, and it holds a genuine Finnish first: it was the country's first lighthouse designed from the outset to run with nobody in it. The light burned acetylene from a tank that had to be topped up once a month. In 1984 it was converted to wind power, and solar panels were added in 1999. It throws its beam twelve nautical miles.

A century after the crown quit, the ore drew people back. Oy Vuoksenniska Ab returned to the deposit in the 1950s and began building a modern mine in 1959; the first load of iron ore concentrate left for Koverhar, near Lappohja, in 1961. It lasted six years. Iron prices were falling while production costs climbed, and in 1967 the mine closed for good, leaving behind a purpose-built village with nobody to live in it. The military then found a use nobody plans for: until 2005 the abandoned buildings served as an urban warfare training ground, which is why so many of the structures standing today are not merely decayed but deliberately half-destroyed. The result is strange enough that the documentary series Abandoned Engineering featured the island in 2019. A coast guard station held on until November 2011; the Finnish Meteorological Institute has run an automated weather station on the island since 1990.

Jussarö is inside Ekenäs Archipelago National Park, which was designated in 1989 around waters protected as a nature reserve since 1956 and which received the European Diploma of Protected Areas in 1996. Part of the island is open to visitors, reached by a scheduled summer ferry from Ekenäs harbour, and there is now a guest harbour, a café, a nature trail and a boat workshop among the wreckage of two failed mining ventures. Two hundred metres to the north lies Lilla Jussarö, a smaller island of a few houses and a harbour, which for a period belonged to Nokia. Landing near the most important bird islands nearby is forbidden between 1 April and 17 July, so that the seabirds get their nesting season undisturbed by anyone at all.