A city with county rights, it is located on the banks of the Tisza river, in the heart of the Great Hungarian Plain, which has made it an important cultural and economic crossroads for centuries.

By the Mesolithic era, the inhabitants of the area had settled into permanent villages, where they practiced agriculture and animal husbandry.

In Tószeg, a neighbor of Szolnok, a large settlement was established, with houses built with thick adobe walls.

The Romans were not able to establish permanent settlements on the Alföld (modern-day eastern Hungary), so in the time before the arrival of the Hungarians in 896, the area was populated by Scythians, Celts, and Sarmatians.

During the building of the Zagyva River dikes, remnants of a Scythian settlement were found, including iron pots and other pottery.

Roman money, weapons, jewelry and pottery are often found; when Szolnok's military airport was enlarged in 1952, over two hundred Gepid and Sarmatian graves were uncovered, which contained rich treasures: gold-plated and decorated fibulas, iron weapons, bone combs, belt buckles, and pots.

In Ó-Szanda, a district of Szolnok suburb Szandaszőlős, archeologists discovered a rich trove of artifacts left by the Gepids, who lived in the area in the 4th and 5th centuries.

The burial grounds found at Rákóczifalva, some 1.5 kilometres (0.93 mi) from Szandaszőlős, show that a large permanent settlement once existed there.

The 11th century saw great improvements in the city due to the Tisza river ferry, customs house, and county business.

During the Mongol invasion of Hungary in 1241 the town was destroyed; it was re-populated under King Béla IV but even by the end of the 14th century it was still considered a village.

King Zsigmond of Luxemburg, in an effort to develop the town, freed Szolnok from certain taxes in 1422, and from customs in 1429.

After the Ottoman armies captured Temesvár and occupied the Danube-Tisza-Maros River area, only two forces of any significance stood between them and the rest of Hungary: Szolnok, and Eger to the north.

Beginning in June 1552, Hungarian, Transylvanian, and Viennese agents all began reporting that the Ottoman army was on the move out of Temesvár towards Szolnok and Eger.

After the fall of other minor fortifications on the Puszta, Sultan Suleiman the Magnificent ordered Pashas Ahmed, Ali, and Mohamed to lead their armies against the castles.

It was in light of this Turkish danger that in 1550-51 Ferdinand I ordered the Szolnok earthworks to be improved with a new town wall (partially planned by István Dobó), the castle to be fortified, and Lőrinc Nyáry put in command.

The original course of the Zagyva has today been filled in, but a small part of it remains as the lake in front of the Szolnok MÁV Hospital.

On the night of September 3, the Hungarian and Spanish horsemen swam across the Tisza, then the boatmen returned for the foot soldiers.

After they departed the front gate was left open until morning, leading to the easy overpowering and capture of Lőrinc Nyáry and the fifty remaining brave men.

In 1553, they established the sanjak of Szolnok, and in the following years built a mosque, baths, and a minaret; during the course of later battles these were destroyed, mostly deliberately.

The remains of the so-called Szolnok Turkish-era Bridge (Hungarian: szolnoki török kori híd) again came to light in August 2003 after a summer of drought.

In 1710, forces loyal to Rákóczi took over the castle, but on October 10, they abandoned it to the advancing army of Imperial General Jacob Joseph Cusani.

After the defeat of the Red Army in July 1919 in the Tiszántúl (the regions east of Szolnok), the Romanians crossed the Tisza and occupied the city.

During World War II, Szolnok was bombed twelve times, mostly by American troops, which caused serious damage to the buildings and the population.

During 1944, it became the location of a "labor camp" and a concentration point for Hungarian Jews being deported to Mauthausen in Austria.

By the end of the war, the majority of the population had fled; the Soviet troops of the 2nd Ukrainian Front found only a couple thousand people when they entered the decimated city on 4 November 1944, in the course of the Budapest Offensive.

The local Municipal Assembly, elected at the 2019 local government elections, is made up of 18 members (1 Mayor, 12 Individual constituencies MEPs and 5 Compensation List MEPs) divided into this political parties and alliances:[10][11] List of City Mayors from 1990: A public transport stop in the Estonian city of Tallinn is named for Szolnok.