According to legend, the inhabitants of the Linth Valley were converted to Christianity in the 6th century by the Irish monk Saint Fridolin, the founder of Säckingen Abbey in what is now the German state of Baden-Württemberg.

Glarus joined the Old Swiss Confederacy in 1352 as one of the foundational eight cantons (Acht Orte) of the period of 1353–1481.

In the early 1840s, after several years of failed crops and as food became scarce, much of the canton found itself deep in poverty.

The Glarus Emigration Society was established in 1844, which offered loans to help residents purchase land in the New World.

[5] The canton of Glarus is dominated by the deep valley of the Linth River and the smaller Sernftal on the east.

The canton contains part of a thrust fault that was declared a geologic UNESCO World Heritage Site, under the name Swiss Tectonic Arena Sardona, in 2008.

The total area of the canton of Glarus is 685 square kilometers (264 sq mi), of which about half is considered productive.

The historical population is given in the following table: The canton's geography helped establish slate works in the 17th century.

Industrialisation also brought cotton printing, hydroelectric plants, metal and machinery factories, and paper mills.