The town gave its name to the
Pays de Gex, at various times under the jurisdiction of France,
Switzerland and the
Duchy of Savoy. The future site of Gex was inhabited around 1800 BC. Around 220 BC, a group of
Gallic warriors known as the
Gaesatae resided in the area around Gex. Afterwards, the town was part of
Roman Gaul. In 1252, Léonette of Geneva, Lady of Gex, descendant of the
count of Geneva,
Amadeus I, married Simon of Joinville, son of
Simon of Joinville and Beatrix of Auxonne, Lady of
Marnay. The city of Gex was included in her
dowry. Later that century, the Joinvilles set up a
castellan and a judge in the town. On November 13, 1353, the town of Gex as well as its castle were captured by
Savoy, and the
pays de Gex was incorporated into the
Savoyard state for nearly two centuries. The
pays de Gex was invaded in 1536 by the
Canton of Bern. The Bernese established a
bailiwick at Gex, managed by a
bailiff. Walls were built in 1550. The
pays de Gex was returned to the
Duchy of Savoy by the treaties of Nyon in 1563 and
Lausanne in 1564. The
Genevans seized it in 1589. Savoy, with the assistance of
Spain, tried several times to take back the
pays de Gex, but they were unsuccessful. During these attacks, the town of Gex was burned in 1590 on July 23 and again on July 30; few of the houses withstood the fires. In 1601, during the reign of
Henry IV, control of the
pays de Gex passed to France as part of the
Treaty of Lyon. With the 1815
Protocol of the Conference of Paris, (signed on 20 November) and the
Treaty of Paris of the same date, Gex was placed in the Customs region of Switzerland and neutralised. The resolutions regarding the Pays de Gex were annulled by Art 435 of the
Treaty of Versailles. In November 1923 France moved its customs office to Gex, and the matter was brought before the
Permanent Court of International Justice (predecessor of the
International Court of Justice), which decided in favour of Switzerland; this case is also notable for being an early example of the doctrine of
fundamentally changed circumstances being invoked before an international court. A compromise was reached in 1932. Historically, citizens spoke a dialect of the
Franco-Provençal language but this dialect is not in use anymore. In 1910 the commune of
Mijoux was created from part of the commune of Gex. ==Population==