It was formed in 1802, when the Subalpine Republic (formerly the mainland portion of the Kingdom of Sardinia) was directly annexed to France.

A provisional department called Eridan was planned in 1799 and established in 1801 in the French-occupied Piedmont.

At the Congress of Vienna, the Savoyard King of Sardinia was restored in all his previous realms and domains, including Piedmont.

The department was subdivided into the following arrondissements and cantons (situation in 1812):[1] Its population in 1812 was 399,237, and its area was 414,526 hectares.

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