Caption: By the 1920s, Milton Hershey had the largest chocolate factory in the world, a thriving model company town, and building projects that included a bank, community swimming pool, amusement park, and multiple golf courses.

Caption: In 1930, American Viscose Corporation opened a new rayon plant in Meadville, PA, about twenty miles south of Erie. Meadville was also the home of Talon Inc., the nation's leading manufacturer of zippers, which in 1940 furnished 5,219 of the city's 9,000 industrial jobs. While the American Viscose Company considered closure of Philadelphia's Marcus Hook plant during the Great Depression, the Meadville plant seemed to lead a charmed life. In fact, Meadville's economy weathered the Depression so well that Time Magazine and New York newspapers were prompted to describe it as "a depression-proof city" whose "streets were paved with gold."

Caption: Located in the Fountain Green section of Philadelphia, the Engel and Wolf's brewery included five large vaults cut out of the solid rock about 45 feet below ground that help their beer at a constant 40 degrees of Fahrenheit. The brewery was situated on the Columbia Rail Road, about a mile above the Fairmount Waterworks.

Caption: Interior of Wanamaker's Grand Depot, ca. 1876.

Caption: Penn Steam Engine and Boiler Works. Foot of Palmer Street, Kensington, Philadelphia. Reaney, Neafie and Co. Engineers, machinists, boiler makers, black smiths and founders, circa 1854.

Caption: After failing to raise funds in Ohio and New York, Charles Hall found willing investors in the thriving industrial center of Pittsburgh, PA. Soon after the beginning of operations on Thanksgiving Day 1888, Hall and his associates at the Pittsburgh Reduction Company turned their focus to the applications for aluminum. In 1901, Hall and his partners formed its own cookware subsidiary, Aluminum Cooking Utensil Company, which soon introduced "WearEver" aluminum cookware, at Wanamaker's Department Store in Philadelphia.

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Caption: Wilcox Paper Mills in Delaware County, PA, as it looked in the 1840s.

Caption: By 1683 William Penn was already operating a tannery in Philadelphia. In the decades that followed the city became a major manufacturer and exporter of leather goods. Indeed, it led the nation in the production of leather until passed by Milwaukee in the early 1900s. The McNeely family operated a leather manufactory in Philadelphia from 1830 into the early 20th century.

Caption: View of the glass works of T. W. Dyott at Kensington on the Delaware near Philadelphia, by W. L. Breton, 1831. Exterior view of Ely Building, constructed in 1829. Image shows Tenth Street facade after the 1845 alterations, designed by architect Napoleon LeBrun, in which a six-columned portico, entablature, pediment, and marble base were added. Building was demolished sometime between 1898 and 1907. Image includes shop of H. Hochstrasser, bell hanger and architectural carver.

Caption: Philadelphia card and fancy printer, on the corner of Fourth and Chestnut Sts.,ca. 1845.

Caption: Bridesburg Machine Works. Alfred Jenks and Son, manufacturers of cotton and wool carding spinning and weaving machinery, shafting and millgearing, Philadelphia, 1856.

Caption: In 1890, George Westinghouse built a plant at Wilmerding, thirteen miles east of Pittsburgh along the PRR's Philadelphia-Pittsburgh main line. Soon, the Wilmerding plant sprawled across thirty acres. By 1905, it employed about 3,000 workers who produced 1,000 sets of brakes every day. William Rau took this photograph of the Westinghouse Air-brake works plant at Wilmerding in 1891.

Caption: In 1875, Andrew Carnegie opened his first steel plant, the Edgar Thomson Works, in Braddock, Pennsylvania. Carnegie named his flagship steel mill after Pennsylvania Railroad (PRR) president Edgar Thomson, his former mentor. Always looking for an advantage, Carnegie located the mill between the PRR and B&O main lines so that the two railroads would reduce their rates to win his business.

Caption: Frank Conrad set up his first radio station in the garage of his home in Wilkinsburg, a small town about 8 miles east of downtown Pittsburgh.

Caption: In 1889, the Duquesne Steel Works opened a state-of-the-art Bessemer steel mill just a short distance up the Monongahela River from Braddock and Homestead. When Carnegie Brothers and Co. purchased the works in 1891, Andrew Carnegie acquired one of the most modern and best equipped steel works in the country.

Caption: In 1917 the Sun Oil Company opened the Sun Shipbuilding and Dry Dock Company to construct tankers for transporting its oil. By the time new ship construction ended in 1977, it had launched 543 vessels, including the spy salvage ship, the Glomar Explorer .