There are several different theories concerning the origin of the city's name.
One is that it comes from Zone Geul-Dagh, the name given to the area by French and Belgian mining companies to refer to the zone near "Geul-Dagh" or Göldağı ('Lake Mountain'), the highest mountain in the vicinity of the Devrek district.
Another theory is that the name originates from the Turkish zongalık which means swamp, or zongura.
Another is that the name may derive from the name of the nearby ancient settlement of Sandraka or Sandràke (in Ancient greek Σανδράκη).
According to another theory the name may have come from the compound word Jangal-Dagh, composed of Persian jangal, which the French entrepreneurs called the area due to its uneven and wooded geography, plus Turkish dağ 'mountain'.
In a 1920 report, the British Foreign Office spelled Zonguldak Zunguldak.
The port city of Zonguldak suffered a heavy bombardment by the Russians during World War I, according to the caption of a Lubok popular print.
As of 1920, the port was under the control of the Heraclea Coal Company. The northern part of the bay featured a man made harbor, for steamship use. At that time, they had two cranes which distributed coal to exporting vessels.
Zonguldak has an oceanic climate (Köppen climate classification: Cfb), closely bordering a humid subtropical climate (Cfa); with high and evenly distributed rainfall the year round. Summers are warm and humid, and the average temperature is around 21 °C in July and August. Winters are cool and damp, and the average temperature is around 6 °C in January and February.
Precipitation is heaviest in autumn and early winter and lightest in spring. Snowfall is quite common between the months of December and March, snowing for a week or two, and it can be heavy once it snows.
The water temperature like in the whole Turkish Black Sea coast is always cool and fluctuates between 8° and 20 °C throughout the year.
The city is the terminus of a railway line to Irmak, with the terminating station Zonguldak Railway Station built in 1937.
Zonguldak is twinned with: Abu Dhabi, United Arab Emirates
New Orleans, LA, United States