During the communist regime, the mines were nationalized by the communist government. Lupeni was declared a city in 1941, at which time it had 12,000 inhabitants. In 1977, Lupeni was the site of the Jiu Valley miners' strike of 1977. After the revolution, in the 1990s, mining operations entered a restructuring process which had a very strong social and economic impact on the city. A large number of mines were closed, and this also affected other related activities, such as suppliers of materials, equipment and services, and agents that operated in the trade and services areas. Nevertheless, in recent years, new areas of economic development emerged, such as tourism, forestry industry, bakery industry, and commerce.