The city was founded in 1721 by Czar Peter I as an ironworking center and was named Yekaterinburg for his wife, who was later proclaimed Empress Catherine I. Industrial development was spurred by the construction of the Great Siberian Highway in the late 18th century and the Trans-Siberian Railroad in the late 19th century. Czar Nicholas II and his family were held captive in the city by the Bolsheviks after the Russian Revolution and were executed here in 1918. The city was renamed Sverdlovsk in 1924 in honor of Bolshevik and Soviet leader Yakov M. Sverdlov. During World War II (1939-1945) industry from threatened European areas of the Union of Soviet Socialist Republics (USSR) was transferred here. Following the disintegration of the USSR at the end of 1991, the city's name was changed back to Yekaterinburg.