In the 16th century, Saint-Étienne possessed an arms factory, and it was this industry which accounted for the town's importance, though it engaged also in the manufacture of ribbons and passementerie from the 17th century (Saint-Étienne was renamed Armeville ("Arms town") during the French revolution because of this activity). Later still it became a coal-mining centre and more recently has been known for the manufacture of cycles. Saint-Étienne was the seat of a post office in 1825 and in 1832, and a relay station in 1832. It did not really develop to any degree until the 19th century.

In the first half of the 19th century, it was only a chief town of an arrondissement in the département of the Loire, with a population in 1832 numbering 19,672 in the east canton and 13,392. Concentration of industry locally prompted these numbers to rise rapidly to 110,000 by about 1880. It was this growing importance of Saint-Étienne that led to its being made seat of the prefecture and the departmental administration on 25 July 1855, Saint-Étienne became the chief town in the département and seat of the prefect, usurping the position which had hitherto belonged to Montbrison. This latter was reduced to the status of a chief town of an arrondissement. Saint-Étienne had absorbed the commune of Valbenoîte and several other neighbouring localities on 31 March 1855.


Recently, in the summer of 2005, the Tour de France passed through St. Etienne. Lance Armstrong won the time trial (contre-la-montre) stage, his only stage win of his 7th and final Tour win.