Over the next one hundred years industrial production grew, and, in 1822 the first coke fired blast furnace in France was constructed.

[1] The company was split as a result of the Alsace-Lorraine region becoming part of Germany after that country's victory in the Franco-Prussian War in 1870.

[1] The Great Depression in France affected the company's ability to invest and in 1948 nine steelmakers formed the Société Lorraine de Laminage Continu (Sollac), pooling their resources to modernise.

Usinor (Union Sidérurgique du Nord) was created in 1948 from the merger of Denain-Anzin (Les Hauts Fourneaux, Forges et Aciéries de Denain-Anzin) founded 1849 and Nord-Est (Les Forges et Aciéries du Nord et de l'Est) founded 1882.

Another factory, dedicated to steel sheet production, was opened in Dunkirk in 1971, receiving materials by sea and from abroad.

The economic effects of the 1973 oil crisis affected both the steelmaking groups, already in debt from modernisation projects, and heavily reliant on state loans; in 1981 both Usinor and Sacilor was nationalised.