Pittsburgh-Des Moines Steel Company

The Pittsburgh-Des Moines Steel Company (originally the Des Moines Bridge and Iron Company), and often referred to as Pitt-Des Moines Steel or PDM was an American steel fabrication company. It operated from 1892 until approximately 2002 when its assets were sold to other companies, including Chicago Bridge & Iron Company. The company began as a builder of steel water tanks and bridges. It also later fabricated the "forked" columns for the World Trade Center in the 1960s, and was the steel fabricator and erector for the Gateway Arch in St. Louis. A number of its works are listed on the National Register of Historic Places.

The company was founded in 1892 by two graduates of Iowa State College, William H. Jackson and Berkeley M. Moss. The partners initially contracted to have their steel tanks fabricated by Keystone Bridge Company of Pittsburgh, but soon took on a third partner, Edward W. Crellin, who was operating a small fabricating shop in Des Moines, Iowa. It was at this point that the Des Moines Bridge and Iron Company was formed. The company would ship steel stock from Pittsburgh for the manufacture of a range of engineered products including water towers, bridges, water works and electric plants. Moss left the company around 1905, after a new fabricating plant had been opened in Warren, Pennsylvania in 1900.

In 1916, the name of the company was changed to Pittsburg-Des Moines Steel Company, and a new headquarters was opened in Pittsburgh. The partnership remained until 1956, when the company was incorporated. It later became Pittsburgh-Des Moines Corporation in 1980, which was later shortened to Pitt-Des Moines, Inc. in 1985. It had also had registered "PDM" as a trademark as early as 1930.

In 2001 the company was acquired by the Chicago Bridge & Iron Company. The Warren plant was closed in early 2009 by CB&I. Also in 2001, the company's steel distribution unit was acquired by Reliance Steel & Aluminum Co.

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