Sarpsborg is one of Norways eldest towns. It was founded in 1016 by Olav Haraldson ("St.Olav"). In the middelage, the town was called Borg. Borg was headseat for both Borgarting and Borgarsyssel. In the 1500-century the town started developping because of the sawmills by the waterfall "Sarpsfossen". But after several attacs from the sueds, the town vas moved to the mouth of Glomma, where Fredrikstad was founded and heritated the trading privilegies. Later, the log running gave foundation of sawmills at "Sarpsfossen", and again people setteld at "Sannesund" a few hundred metres downstream from the waterfall. "Sannesund" is as close to the waterfall as ships can go.
In 1839 Sarpsborg was given back its trading privilegies. The industrial developpement has given the town its financial founding, and today several types of industri has settled here. Due to this industry, we tow manors was built in Sarpsborg, Borregård manor and Hafslund manor. And both Borregård and Hafslund are well-know industrial companies today as well.
Here are some links reletated to Sarpsborg:
In the middelage, Borgarting was the headseat of Borgartingslag, a "leagal aerea" consisting of the aerea round the Oslofjord (among others; Ranrike, Vingulmork and Vestfold). The headseat was placed in Borg (now Sarpsborg), and it is supposed to be founded by Olav Haraldsson. In the 1000-century, Borgarting was mentioned as a place to tribute the kings, but in 1224 it is mentioned as as "leagal headseat".
Borgarsyssel was, in the middelage, an aerea (covering todays Østfold), lead by a district governor. The headseat was Borg. Borgarsyssel is now the name of the folk museum in Sarpsborg.