Title: Youngstown, Ohio
Content:  such as Chicago, Pittsburgh, Akron, or Cleveland. Hence, when economic changes forced the closure of plants throughout the 1970s, the city was left with few substantial economic alternatives. The September 19, 1977, announcement of the closure of a large portion of Youngstown Sheet and Tube, an event still referred to as "Black Monday", is widely regarded as the death knell of the old area steel industry in Youngstown. In the wake of the steel plant shutdowns, the community lost an estimated 40,000 manufacturing jobs, 400 satellite businesses, $414 million in personal income, and from 33 to 75 percent of the school tax revenues. The Youngstown area has yet to fully recover from the loss of jobs in the steel sector.
Title: Economy of Youngstown, Ohio
Content:  Sheet and Tube instantly put 5,000 workers out of work. The day is still known locally as "Black Monday". Youngstown Sheet and Tube's announcement had a ripple effect in the area. In 1979–1980, U.S. Steel pulled out of the Youngstown area and started scaling back its operations in Pittsburgh before eventually merging with Marathon Oil and filing with bankruptcy. In the mid-1980s, Republic Steel also filed for bankruptcy. Attempts to revive the local steel industry proved unsuccessful. Shortly after the closure of most of Youngstown Sheet and Tube's area operations, local religious leaders, steelworkers, and activists such as Staughton Lynd participated in a grassroots effort to purchase and refurbish one of the company's abandoned 
Title: Economy of Youngstown, Ohio
Content:  The economy of Youngstown, Ohio, flourished in the 19th and early 20th centuries, with steel production reaching all-time highs at that time. The steel boom led to an influx of immigrants to the area looking for work, as well as construction of skyscrapers in the area. The city's population peaked at 170,002 in 1930, just at the onset of the Great Depression. World War II also brought a great demand for steel. After World War II, demand for steel dropped off dramatically, and industrial base of Youngstown began to see a decline. Youngstown's economy has been impacted by a loss of the steel industry jobs which started on September 19, 1977, on what became known to locals as "Black Monday", and continued into the mid-1980s. While the loss of steel industry jobs in the region coincided with the general deindustrialization of Rust Belt cities such as Youngstown as well as the United States as a whole, Youngstown's economic struggles have been well documented. In the Mahoning Valley region, where Youngstown is located, the city's population was halved, while non-industrial businesses were forced to close or relocate due to cascading effects resulting from Youngstown's deindustrialization.
Title: Youngstown, Ohio
Content:  Endowed with large deposits of coal and iron as well as "old growth" hardwood forests needed to produce charcoal, the Youngstown area developed a thriving steel industry, starting with the area's blast furnace in 1803 by James and Daniel Heaton. By the mid-19th century, Youngstown was the site of several iron industrial plants, and because of easy rail connections to adjacent states, the iron industry continued to expand in the 1890s despite the depletion of local natural resources. At the turn of the 20th century, local industrialists began to convert to steel manufacturing, amid a wave of industrial consolidations that placed much of the Mahoning Valley's industry in the hands of national corporations. In the late 1930s, the community's steel sector 
Title: Economy of Youngstown, Ohio
Content:   Between the 1920s and 1960s, the city was known as an important industrial hub that featured the massive furnaces and foundries of such companies as Republic Steel and U.S. Steel. At the same time, Youngstown never became economically diversified, as did larger industrial cities such as Chicago, Pittsburgh, Akron, or Cleveland. Though population levels remained flat for a few more decades, population had not grown since the Great Depression, though General Motors had opened Lordstown Assembly in 1966 to help offset some losses. Hence, when economic changes forced the closure of plants throughout the 1970s, the city was left with few substantial economic alternatives. The 1969 corporate merger between the Youngstown Sheet and Tube Company 
Title: Economy of Youngstown, Ohio
Content:  Founded by John Young in 1797 in the Connecticut Western Reserve section of the Northwest Territory, Youngstown spent the first half of the 19th century as a small village, dependent on mostly agricultural needs, until the beginning of the Second Industrial Revolution. The discovery of iron ore along the Mahoning River, however, would make the city a viable and logical place to manufacture steel. The city sits roughly in between Cleveland and Pittsburgh—steel manufacturers in their own right—and halfway between New York City and Chicago. Youngstown Sheet and Tube and Republic Steel were among the region's largest locally owned steel companies, while U.S. Steel also had major operations in the region.  Endowed with 
Title: Mahoning Valley
Content:  plant closure occurred on September 19, 1977, when Youngstown Sheet and Tube abruptly closed its Campbell Works and furloughed 5,000 workers. Today the area produces little steel, and is home to many scrap metal yards and aluminum plants. A 2009 documentary titled "Steel Valley: Meltdown" describes "the past, present and future of the Mahoning Valley" through the eyes of local experts, including one local organizer who stated, "We are the first generation completely removed from the days when steel mills were active." The Mahoning Valley Economic Development Corporation, founded in 1979, is active in economic revitalization and diversification. It owns two industrial parks, and has purchased local rail lines, including the Youngstown and Austintown Railroad and the Warren and Trumbull Railroad.
Title: Youngstown Sheet and Tube
Content:  closed its Campbell Works and furloughed 5,000 workers on September 19, 1977, a day remembered locally as "Black Monday." The Brier Hill Works and the company's plants in Indiana were sold to Jones and Laughlin Steel, later acquired by Ling-Temco-Vought (LTV), a conglomerate. The Brier Hill Works closed in 1979 as part of a continued wave of steel mill closings that devastated the Youngstown economy. The Brier Hill Works was eventually reopened in 1986 by Cargill Corporation, under the name North Star Steel. In 2002, Cargill sold the operations to recycling minimill Vallourec Group, a French conglomerate. The Indiana Harbor mill continues operating, owned by Cleveland-Cliffs.
Title: Economy of Youngstown, Ohio
Content:  the New Orleans-based Lykes Corporation proved to be a turning point in the demise of the local steel industry. The merger and subsequent takeover of Youngstown Sheet and Tube burdened the community's primary steel producer with hundreds of thousands of dollars in debt. Further, the deal placed control of the company outside of the Mahoning Valley. On September 19, 1977, it was announced a large portion of Youngstown Sheet and Tube would be closing. Although federal laws now require employers to give 60 days notice to its employees if they plan on doing mass layoffs, the Worker Adjustment and Retraining Notification Act was still eleven years from going into effect at the time, and 
Title: Economy of Youngstown, Ohio
Content:  a pedestrian-oriented plaza, was reopened to through traffic. The downtown area has also seen the razing of structurally unsound buildings and the expansion or restoration of others. New construction has dovetailed with efforts to cultivate business growth. Reversing the trend, in 2010, Vallourec & Mannesman broke ground for a $620 million-dollar pipe mill north of its existing business V&M Star. Production of steel pipes began in October 2012. Opened in 2012, the facility is 1 e6ft2 in area and produces tube goods to service natural gas exploration in the Marcellus Formation and has been an employer for 350 people.

Question: when did the steel mills closed in youngstown ohio?
Answer: September 19, 1977.