It owns about 140 kilometres (86 miles) of track, connecting the principal towns of Wernigerode, Nordhausen and Quedlinburg and several smaller settlements in the area.

The company runs a significant number of its trains with steam haulage, mostly employing 1950s vintage 2-10-2 tank locomotives, hauling traditional open-platform bogie carriages.

The so-called Trans-Harz Railway (Harzquerbahn) from Wernigerode via Drei Annen Hohne to Nordhausen was fully opened to traffic on 27 March 1899.

Shareholders in the HSB are the districts of Harz and Nordhausen, the communes along the railways, the town of Quedlinburg, the municipality of Tanne and the spa company of Braunlage.

Today the HSB has the longest single network of narrow gauge railway in Germany, with a total length of 140.4 km (87 miles), 44 stations and halts.

Its trains run daily to a timetable and it operates more than ten steam locomotives, seven diesel railbuses and three trams (on the Nordhausen Tramway).

Since then, the above-mentioned tramway between Nordhausen Hospital and the HSB halt of Ilfeld-Neanderklinik (Line 10) has been worked by electric and hybrid vehicles of the Combino duo class.

On 18 April 2005, work started on the extension of the Selke Valley Railway from Gernrode to Quedlinburg (length 8.5 km) after DB AG had closed this standard-gauge section and sold it to the HSB.

In 2009 Lower Saxony tried to co-finance a connection of the town of Braunlage to the HSB network using an accumulation of capital from the economic stimulus package, Konjunktur II.