In the 17th century rich and high-quality mineral deposits were discovered in the Ural region. First iron and copper smelters were founded by the mid-17th century. The area was recognized by the Russian government as a strategic source of raw materials. More than 60 factories were built in the first half of the 18th century and this number doubled in the 1750–60s. The industrial activity declined in the early 19th century due to the crisis of the feudal system in Russia, and the growth slowed in all areas except for the gold mining. The largest industrial and commercial centers were Perm, Yekaterinburg, Orenburg, Ufa, Kungur and Irbit. Irbit hosted the biggest fair of the Urals. In the 1840s, regular commercial navigation started on the Kama River.