The city of Kilkis, the capital of the prefecture, is a city rich in history. It is built at the foot of the hill of St. George, on top of which stands a post-Byzantine church. Located at a distance of 48 km. from Thessaloniki and 550 km. from Athens, it has considerable industrial development with a highly active industrial area (BI.PE. Stavrohori).
In 2011 (National Statistics Agency census), the city had a permanent population of 22.740 and the Municipality had 51.710 residents. The residents of Kilkis are engaged in agriculture and stockbreeding, while the establishment of the Industrial Area in Stavrohori has attracted many young scientists and workers during the recent decades.
The name of Kilkis comes from the Roman period (1st century AC), when the Callicum (or Gallicum) was established in this area.
Callicum or Kallikos was the leather sieve which was used to collect the gold from the River Ehedoro or "Gallikos River", a name derived from the same establishment, Kallikos. Today, Kallikos settlement has been equated with the Colchida of Kilkis, where there are ruins of Roman and early Christian settlements.
With the establishment of the Bulgarian state during the 10th century, Kilkis was destroyed and its inhabitants migrated to southern Italy. After 1014, with the destruction of the Bulgarian army by the Byzantine emperor Basileio II, the city was rebuilt. During the 14th century, the area belonged to landowners of Byzantium, referred to as "Gallikos property." During the Ottoman rule, the city is known as Kilkisi and in the 15th Century gains political stability and prospers in the fields of textiles and silk. In the early 17th century, it belonged to the manor of Giourouk Hassan Aga, while in 1765 it was incorporated into the manor of Abdul Aga, from the family of landowners Champenteroglou of Doirani. In 1780, the area was offered to Yusuf Bey, of the family Evrenos.
The people of Kilkis participated in the Revolution of 1821 with Zafirios Stamatiadi from Idomeni as the leader, and the Macedonian Struggle (1904-1908) with the Macedonian Fighters M. Sionidis, I. Ramnalis, C. Doitsinis and others. Eventually, the area was released in 1913 (Second Balkan War), after the glorious three-day battle of Lachanas (June 19-21). The population exchanges with Bulgaria (1919), Turkey (1923) and the settlement of the refugees from Eastern Thrace, Anatolia, Cappadocia and Pontos follow. During the Second World War, the area came under the German occupation and faced the Greek Civil War.
These days, Kilkis is a growing modern city with good infrastructure and an ideal size for quality of life, as one can combine the rich and beautiful nature of the area with the urban routine, without dealing with the crippling rhythm of a megacity.