For more than 50 years, in the dozen or so red brick buildings at the Pittsburgh Locomotive Works on the North Side, men made steam engines for railway companies all across America and beyond.

In the carpenter and pattern shop, iron and brass foundries, machine shop, engine room, smith shop, paint shop, flask shop, cupola house, boiler shop and other smaller buildings, men worked to design and produce locomotive engines -- some 2,400 of them by the time the company merged with seven other plants to form American Locomotive Co. in 1901.

Now demolition has begun on the former locomotive works buildings, long owned by Duquesne Light, and this year all of them will come down. The utility, which had used them for storage and office space, moved its employees out last summer.

"It is in a very poor state of disrepair," said company spokesman Joseph Vallarian. "It's becoming dangerous" for employees.

The cluster of buildings, bounded by Beaver, Island and Preble avenues and Seymour Street in the Chateau district, is a relic of Pittsburgh's great industrial and manufacturing era, a time when the city produced not only iron and steel but also the products made from them: wheels, axles, hydraulic jacks, plumbing fixtures, steamboats, cooking stoves, iron beds, bridges, streetcars and more.

The locomotive works buildings are closely associated with one of America's greatest industrial giants before his ascendancy as a steel manufacturer. Andrew Carnegie's long involvement in railroads began in 1853 when, as a teenager, he became personal clerk and telegraph operator for Thomas A. Scott, later president of the Pennsylvania Railroad. By the late 1850s, Carnegie was superintendent of the railroad's Pittsburgh Division.

During the Civil War, when the need for trains and safe rails was high, Carnegie organized a rail-making company, the Superior Rail Mill and Blast Furnaces, along the Ohio a few blocks from where the locomotive works would be built. Around the same time, he established two iron mills in the Strip District.

With the demand for locomotives also great, Carnegie founded the Pittsburgh Locomotive Works with Thomas N. Miller, one of his iron mill partners, in 1865; by spring of 1867, it had produced its first steam engine. The company soon had a reputation for building a quality product, and its locomotives pulled trains on many of the country's most prominent railroads, from the Baltimore & Ohio to the Acheson, Topeka & Santa Fe, from the Manhattan Elevated to the Union Pacific. Pittsburgh engines also headed up trains in Japan and Central and South America.

Carnegie's company was the earliest of three locomotive manufacturers here, including H.K. Porter & Co., which made light-duty locomotives in Lawrenceville, and Westinghouse Machine Co. in the Strip District. Those manufacturers' buildings survive.

As superintendent and later general manager, the young and energetic Daniel A. Wightman guided production at Carnegie's plant for more than 30 years.

"Pittsburgh Locomotive Works was one of the first to produce really huge locomotives," according to the website of the Smithsonian Institution Archives Center, where the company's records are housed. Among them are Wightman's sketchbook of the mid-1870s and 311 blueprints of engine designs and drawings.

Wightman left the firm in 1900, the year before it became part of the American Locomotive Co., known as ALCO.

Walter P. Chrysler, former railroad machinist and future automaker, joined ALCO as works manager in 1909 and put the then-struggling Pittsburgh plant back on track before leaving for his first job in the auto industry -- works manager for a Buick plant -- in 1912.

Thousands of skilled workmen labored at the locomotive works over the decades; at full capacity the plant employed as many as 1,500. Some lived nearby in the Manchester neighborhood, which built up rapidly in the late 19th century with factories and housing, and attended St. Andrew Church, once located across from the locomotive works on Beaver Avenue.

Over the years, and with the construction of elevated Ohio River Boulevard next to the factory, the buildings lost all of their residential context. Today, they're surrounded by Duquesne Light equipment and a chain-link fence.

American Locomotive Co. closed the Pittsburgh plant in 1919. At least three of its locomotives are preserved and on view, none in Pittsburgh. One is at a park in Buffalo, Wyo.; another at the Canadian Railway Museum near Montreal; and a third at the Lake Superior Railroad Museum in Duluth, Minn. At the latter is an engine built in 1906 for the Duluth, Missabe and Northern Railroad. It was sold to the Duluth & Northeastern in 1955 and used to haul logs, lumber products and general freight until 1964.

A historic map shows the Pittsburgh Locomotive Works buildings were owned by Duquesne Light Co. as early as 1925. Some of them retain their original overhead track systems.

"We still used that to move things when we needed to," Mr. Vallarian said.

The buildings are not mentioned in any of the books documenting historic architecture here, perhaps because their significance is more cultural than architectural. The most prominent and distinguished is the former office building, with its intricate brick detailing and round corner tower.

While the demise of historic industrial buildings is almost always regrettable, the loss of these buildings, because they're in an isolated industrial district, will not be keenly felt by many. Yet their passing is worth noting, and only partly because what replaces them may well be an eyesore.

When they come down, Duquesne Light will use the vacant land for storage of transformers and large spools of wire and for parking.

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