Population in January 2011 was 1,206 but the town has been shrinking in size since the 1950s when the town reached its peak with 3,000 inhabitants.
The municipality of Ólafsfjörður and Siglufjörður merged to form a municipality called Fjallabyggð, which literally means Mountain Settlement.
The town grew up around the herring industry that was in much bloom in the 1940s and 1950s, but the herring are gone now.
Siglufjörður was connected with a road for the first time in 1940, when the horse riding trail through Siglufjarðarskarð was improved enabling cars to get through. Before, ships, seaplanes, horses and strong legs provided the transport.
Today the town remains dependent on fishing industries although the herring are gone. The government of Iceland is attempting to reverse the population shrinking in the area by improving land transportation. Two road tunnels were dug between Siglufjörður to the neighbouring town of Ólafsfjörður to connect with the region of Eyjafjörður in the east. These tunnels are called Héðinsfjörður Tunnel and their total length is 11 km (6.8 mi). They were opened on October 2, 2010. Siglufjörður was already connected by the 800 m Strákar Tunnel to the west; it used to be the town's only road connection open whole year around. The tunnel was completed in 1967 and before that the only road to the town was a narrow mountain pass, open only during the summer.
The old road to Siglufjörður is open during the summer. The road was and still is the highest mountain road in Iceland and is used today both for hiking, horseriding and pleasure driving.
One of the aspects of the new tunnel to Héðinsfjörður, is that it will open up interesting mountain tracks, trout fishing opportunities etc., which so far have only been open to boat owners or those willing to walk the old trail over the pass between Siglufjörður and Héðinsfjörður.
There have not been regular flights to Siglufjörður for many years, but private small planes make frequent landings. The closest airport with scheduled flights is in Akureyri, an hour's drive from Siglufjörður.
Siglufjörður experiences midnight sun from 9 June until 1 July.
Although Siglufjörður doesn't experience polar night in December solstice, but the shortest daylight hours in Siglufjörður is 2 hours 39 minutes, from 11:54 UTC until 14:33 UTC on 21 December.