Similarly to most
urban centers in Moldavia, Bacău emerged on a
ford that allowed water passage. There is archaeological evidence of human settlement in the centre of Bacău (near
Curtea Domnească) dating from the 6th and the 7th centuries; these settlements were placed over older settlements from the 4th and the 5th centuries. A number of vessels found here are ornamented with crosses, hinting that the inhabitants were
Christians.
Pechenegs and
Cumans controlled the Bistrița valley during the 10th, 11th and 12th centuries.
Colonists played a significant role in the development of the town. Archaeological finds, some surface or semi-buried dwellings from the second half of the 15th century, suggest that
Hungarians started to settle in the region after 1345–1347 when the territory was under the control of the
Kingdom of Hungary. They mainly occupied the flat banks of the river Bistrița. Discoveries of a type of 14th-century grey ceramic that has also been found in
Northern Europe also suggests the presence of
German colonists from the north. Originally the town focused around the
Roman Catholic community that settled near a regular local
market frequented by the population of the region on the lower reaches of the river. The customs house in the town is mentioned in
Old Church Slavonic as
krainee mîto ("the customs house by the edge") in the document which may indicate that it was the last customs stop before Moldavia's border with
Wallachia. An undated document reveals that the
șoltuz in Bacău, that is the head of the town elected by its inhabitants, had the right to sentence felons to death, at least for robberies, which hints at an extended privilege, similar to the ones that royal towns in the Kingdom of Hungary enjoyed. Thus this right may have been granted to the community when the territory was under the control of the Kingdom of Hungary. Alexander the Good donated the wax collected as part of the tax payable by the town to the nearby
Eastern Orthodox Bistrița Monastery. It was most probably his first wife named Margaret who founded the
Franciscan Church of the Holy Virgin in Bacău. The letter also reveals that
Hussite immigrants who had undergone persecutions in
Bohemia,
Moravia, or Hungary were settled in the town and granted privileges by Alexander the Good. The monastery of Bistrița was also granted the income from the customs house of Bacău in 1439. In 1435
Stephen II of Moldavia (1433–1435, 1436–1447) requested the town's judges not to hinder the merchants of
Brașov, an important center of the
Transylvanian Saxons in their movement. From the 15th century
ungureni, that is
Romanians from Transylvania began to populate the area north of the marketplace where they would erect an Orthodox church after 1500. It was rebuilt and extended under
Stephen III the Great of Moldavia (1457–1504) who also erected an Orthodox church within it. Thus the local princely residence was abandoned after 1500. The town was invaded and destroyed more than one time in the 15th and 16th centuries. The customs records of
Brașov shows that few merchants from Bacău crossed the
Carpathian Mountains into Transylvania after 1500, and their merchandise had no particularly high value which suggests that the town was declining in this period. From the early 17th century the bishops of Bacău were Polish priests who did not reside in the town, but in the
Kingdom of Poland. They only travelled time to time to their see in order to collect the
tithes. But the Polish bishop protested against the agreement and the
Holy See also refused to ratify it. Due to the frequent invasions by foreign armies and plundering by the
Tatars in the 17th century, many of its Catholic inhabitants abandoned Bacău and took refuge in Transylvania. But in 1851 the Catholic congregation in the town still spoke, sang, and prayed in
Hungarian. The first
paper mill in Moldavia was established in the town in 1851. The town was declared a
municipality in 1968. ==Climate==