Edgar Thomson Steel Works

Location: Braddock, PA near Pittsburgh
Category: Steel Mill

Related Job Sites

Mon Valley Works – Edgar Thomson Plant

United States Steel Edgar Thomson Works

Edgar Thomson Works, now owned by U.S. Steel, was built in 1874 by Carnegie, McCandless & Company. The land where it was built was purchased by one of the partners of the firm for $219,003.30. After discovering the Bessemer steel making process in Europe, Andrew Carnegie decided to open a plant in Braddock. Braddock was the perfect location because it was near both the Baltimore and Ohio (B&O) and Pennsylvania Railroad lines. It was also near the area where the Monongahela and Allegheny Rivers meet to make the Ohio River. It was easy to transport raw materials to the plant and finished product away from it.

Edgar Thomson was chosen as the name because it was the name of the president of the Pennsylvania railroad at the time, and the partners were hoping the railroad would be a big customer of the mill. Carnegie knew that railroads and bridge makers were asking for more steel instead of iron, the less refined product that becomes steel. After his trips to Europe, Carnegie knew that the Bessemer steel making process reduced production costs of steel, so he studied the process. Bessemer converters were egg-shaped vats that held molten iron, and cold air was blown into the bottom, which removed impurities and carbon from the iron. It reduced the amount of time it took to make steel, allowing larger amounts to be produced by unskilled workers. This made steel production much cheaper and easier.

The mill was able to capitalize on limited money in the market, which allowed the plant to acquire equipment and materials at a reduced cost. Carnegie hired a man named Alexander Holley to be the plant’s engineer. He worked with Cambria Iron Company previously and was known as an expert in the Bessemer process. Holley improved the Bessemer process, making the plant a world-renowned facility. He did this by creating a swappable converter bottom. Typical bottoms would break down quickly, needing to be replaced. The entire converter would have to cool down before the bottoms could be replaced, slowing down production capacity.  With the swappable converter bottom, workers could replace the bottoms without cooling the entire container. After opening, the mill could create 225 tons of steel rails every day. Multiple generations of families would go on and work at the mill. As technology improved, Carnegie would invest in the latest equipment. He was able to reduce labor costs and maintain the most productive facilities in the world.

The addition of Edgar Thomson to Braddock completely changed the town. It was once an agrarian community named after the site where General Edward Braddock was killed in the French and Indian War. Many immigrants from around the world settled in Braddock to work at the mill. Generally made up of African Americans, and Italian and Eastern/Northern European decent, these workers lived in tenement housing around the mills.

The influx of population caused merchants and entrepreneurs to flock to the area to open restaurants, saloons, and general stores. Early life in Braddock was mostly tied to steel mill working hours. In 1901, new land was acquired and nine new blast furnaces as well as two ingot mold foundries were installed.  In the 1930s, the Bessemer process became obsolete, so U.S. Steel turned to open heath furnaces. These furnaces create  tremendous amounts of heat, (upwards of 3,000 degrees), by utilizing waste gases to increase heat production. Workers dealt with high temperatures in the mill because of the furnaces. If there was water in molds, the molten metal would explode and molten metal would go everywhere. The 16 furnaces they had could produce 40 tons of steel every six hours. Open hearth furnaces became obsolete in the 1980s, and now the plant uses blast furnaces to create steel. Newer processes only take a tenth of the time to make steel, reducing the amount of energy it takes to melt raw materials. This creates significant time and cost savings, which is why the industry pivoted to these types of furnaces. Iron ore, coke, and limestone are heated under pressure and melted to produce steel in this steel making process.

In the 1970s and 1980s American steel production began to decline. There was not much technological innovation and companies had to compete with foreign steel producers. By 1982, production capacity for steel in the United States was reduced to 50 percent. Steel shipments reduced from 87 million tons in 1981 to 62 million tons in 1982. Almost 450,000 steel workers around the country were laid off, with close to half never working in the industry again. Many steel plants owned by US Steel closed, but Edgar Thomson survived. In the 1980s, U.S. Steel reduced production at the plant because of a decline in the automotive and appliance markets. At the time, the plant created nearly 16 percent of all steel produced for the company. Before this occurred, Edgar Thomson was closed for a three-month period the first time since the late 1800s due to financial reasons.

The Edgar Thomson plant still operates today. It creates steel slabs that are then turned into sheet products that are used by the appliance, automotive, metal building, and home construction industries. It does this with two blast furnaces, two top-blown basic oxygen process vessels, a vacuum degasser, ladle metallurgy facility, and a dual strand continuous slab caster.  The plant is modernized and automated, and has 400 employees. Edgar Thomson is part of the Mon Valley Works, which makes up to 2.9 million metric tons of steel every year. U.S. Steel planned a $1 billion upgrade to Edgar Thomson in 2021, but it later decided against this. The plan was to install an endless casting mill, which would allow the company to make more steel with less emissions. The company cited that plans on becoming carbon neutral by 2050 were the reason for the cancellation. U.S Steel also had plans to allow fracking at the Edgar Thomson plant, which ultimately fell through. It reached an agreement with Merrion Oil and Gas from New Mexico to drill and frack a well at the site. There were many years of opposition from residents in the area.

Buildings, Departments, and Equipment Found at Edgar Thomson:



Blast Furnaces

Cast Houses

Boiler house

Engine House

Pump House and Tank

Offices and Laboratory



Locomotive House

Converting Department

Blowing Engines and Pumps

Converting House

Ladle House

Bottom House


Electric Light House

Baker Blowers

Old Rail mill

Ingot Furnaces

Blooming Mill

New Rail Mill

Bloom Furnaces

First and Second Roughing Trains

Finishing Train

Hot Saws

Hot Beds

Straitening and Drill Presses

Loading Beds

Roll Shop




Machine, Carpenter, and Pattern Shops

Manganese Shed

Limestone Crusher

Open Hearth Furnaces

Slab mill

Forging Mold Foundry

Basic Oxygen Furnaces

Mixer Baghouse

Continuous Caster Mill

Ladle Metallurgy Facility

Vacuum Degasser

Riley Boilers

Vessel (Steelmaking furnace)

Casthouse Baghouse

BOP Fugitive Baghouse

BOP Scrubber

Water Cooling and Treatment Facilities

Jobs associated with Edgar Thomson:

Pipe fitter: Workers that lay out, install, maintain, and repair pipelines, fittings, and fixtures for plant maintenance and construction.

Machinist: workers that operate machinery. They do this by setting up all machines and do all the layout, fitting, and assembly work.

Boilermaker: Assemble, install, maintain, and repair boilers or large vats that hold liquids and gases.

Welder: Assemble metal (brazing), cut metal, or repair damage to metal by using high heat.

Blacksmith: Forge, hammer weld, and heat treat iron and steel products for construction, maintenance of plant equipment.

Millwright: Maintains mechanical equipment by inspecting, repairing, replacing, installing, and adjusting equipment in a certain area.

Bricklayer: Performs masonry work, lays brick in maintenance and construction of plant.

Motor Inspector: Performs inspections, repairs, replacement, installation, adjustment, and maintenance of electrical equipment of plant and plant itself.

Blast Furnace:

Stove Tender: Operates the stoves of blast furnaces. Maintains heat, adjusts temperature when necessary.

Keeper: Helps prepare blast furnace casting and flushing operations.

Pig Machine Operator: Operates the crane that pours molten metal (jib crane)

Topman: Cleans the tops of blast furnaces, water scale, and platforms of furnace tops.

Skull Cracker Craneman: Operates the skull cracking crane, which is a crane used to break up solidified metal (skulls) from the ladles and runners of the steel works.

Open Hearth Furnace:

Charging Machine Operator: Operates the charging machine (machine that moves scrap metal, known as charge) into the hearth furnace.

First Helper: Operator of the open-hearth furnace.

Stripper Craneman: Operates the overhead electric traveling crane.

Cold Strip and Sheet Mill:

Batch Pickler: Carries out pickling metal, which is the process of removing impurities like stains, inorganic contaminants, rust, and scale from the metals.

Flying Shearman: Operates the flying shear, which is a machine that cuts the continuous steel sheet at the same speed as the production line. Performs the slitting and end shearing of the continuous metal into steel sheets.

Shot Blaster: Operates the shot blaster, which removes scale and prepares the metal for coating.


Babbittman: Melts and pours babbitt, which is an alloy of copper, tin, antimony, and sometimes lead. It is used on axles, bearings, and crankshafts as a lubricant and to prevent corrosion.

Plate Mill:

Salt Thrower: Throws salt onto slabs of metal to remove the scale off the hot metal right before it enters the plate mill rolls.

Bloor, Slab, and Billet Mills

Cinderman: Removes cinder (byproduct of coal burning) from under boiling pits (hold steel to equalize temperature before being rolled.)

Blooming Mill Roller: Controls the blooming mill, which processes ingots into slabs and blooms.

Hooker: Operates the hook used to carry and move metal products.

Scarfer: removes any defects on billets, slabs, and blooms by burning them with a torch (called scarfing), also checks for and marks any surface defects on metals.

Multiple professions at steel mills worked with asbestos. The occupations most at risk of working with asbestos were machinists, pipefitters, and boiler workers. Other workers who regularly were exposed to asbestos were welders, blacksmiths, bricklayers, millwrights, and motor inspectors. Anyone who was exposed to machinery, equipment, and materials in a steel mill were also at risk of asbestos exposure. To protect workers from heat, asbestos was present with ovens, hot blast stoves, furnaces, rolling mills, tanks, boilers, cranes, molding boards, and steam pipes. Workers could also have worn asbestos- based protective clothing including mitts, coats, leggings, aprons, coveralls, and face masks. Other protective materials like asbestos blankets to cover ladles, refractory bricks, floor and ceiling tiles, and liner boards were a source of asbestos exposure.

Specific products containing asbestos include floor tiles, ceiling tiles, liner boards, refractory bricks, and asbestos cement. Asbestos- based insulation was also heavily used to protect workers from heat and fire. Insulation could be found on ovens, hot blast stoves, furnaces, rolling mills, tanks, boilers, cranes, molding boards, and steam pipes. The most common asbestos insulation was asbestos packing, pipe wrap insulation, and asbestos cement. Machine parts including brake pads, clutches, gaskets, valves, and pumps had asbestos fibers to reduce heat and prevent damage to parts that withstand high temperatures. Steel molds were also made of asbestos because they could withstand high heat.


“Alexander L. Holley” National Inventors Hall of Fame [Link]

Amy McKeever, “In the Shadow of the Steel Mill” Topic (August 1, 2018). [Link]

“Basic Oxygen Furnace” Science Direct [Link]

“Blast Furnace” Science Direct [Link]

Carnegie Brothers & Company, “The Edgar Thomson Steel Works And Blast Furnaces” [Link]

“The Edgar Thomson Steel Works and Blast Furnaces” Norman B. Leventhal Map & Education Center [Link]

Hugh P. Meese, “EDGAR THOMSON STEEL WORKS” [Archive Link]

“Made in America: The Past, Present, and Future of the Steel Industry” Boyd Metals [Link]

Reid Frazier, “US Steel drops plan for fracking at steel mill State impact Pennsylvania (April 27, 2021). [Link]

Robert McNamara, “The Bessemer Steel Process” ThoughtCo. (April 1, 2019). [Link]

“The Steel Business” American Experience [Link]

“Steel Production” American Iron and Steel Institute [Link]

“U.S. Steels Footprint” U.S. Steel [Link]

“Workers” Rivers of Steel Heritage Area [Link]


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