The archaeological evidence indicates no settlements in Bern area prior to 12th century. A Celtic oppidum stood on the peninsula north of Bern, fortified since the second century BC (late La Tène period), which is thought to be one of the 12 oppida of the Helvetii mentioned by Caesar. During the Roman era, a Gallo-Roman vicus was on the same site. The Bern zinc tablet has the name Brenodor ("dwelling of Breno"). In the Early Middle Ages, a settlement in Bümpliz, now a city district of Bern, was locate 4 km rom the medieval city.

The medieval city of Bern was founded by the Zähringer ruling family, which rose to power in Upper Burgundy in the 12th century. According to Cronica de Berno historiogrpahy (1309), Bern was founded in 1191 by Berthold V, Duke of Zähringen. In 1218, Bern was made a free imperial city by the Goldene Handfeste of Holy Roman Emperor Frederick II.

In 1353, Bern joined the Swiss Confederacy, becoming one of the eight cantons of the formative period of 1353 to 1481. Over the course of the 14th and the 16th century, Bern significantly expanded its territory both by conquest and purchase. Notably, Bern invaded and conquered Aargau in 1415 and Vaud in 1536, thereby becoming the largest city-state north of the Alps. By the 18th century, it comprised most of what is today the canton of Bern and the canton of Vaud.
In 1798, with the establishment of the Helvetic Republic, Bern was divided, the canton of Oberland with Thun as its capital and the canton of Léman with Lausanne as its capital were detached from what was left of the Canton of Bern. With the post−Napoleonic Restoration of 1815, Bern acquired the Bernese Jura with Biel/Bienne from the bishopric of Basel, while the canton of Léman became the canton of Vaud and remained separate from Bern. In modern days, in 1979, parts of the Bernese Jura were separated from Bern to form the new 26th canton of Jura. In 1994 the Laufen District was transferred to the canton of Basel-Landschaft.

Swiss History Timeline - Bern
Bern coat-of-arms