class manufacturer, as Sharples continued to manufacture De Laval separators, and also selling machines of his own design. Lawsuits for patent infringement were filed by De Laval in 1891, but Sharples won in US federal court by claiming that his improvements were significant. He applied for and got his own cream separator patent in 1897, in all, 23 more lawsuits were filed against him between 1890 and 1919.

founded Chester County Mushroom Laboratories in 1928. They built a small plant on East Rosedale Avenue to produce spawn and provide testing services to area mushroom growers. One of their early successes was collaborating with frozen foods pioneer Clarence Birdseye (yes, the same Birdseye on the label of the peas and corn in your freezer) on a process used for freezing mushrooms.

Nonetheless, Sharples expanded, introducing automatic fire alarms, electric lighting, color print advertising, and a steam whistle that could be heard all over the Borough. In the decade before World War I, Sharples built the Farmers & Mechanics Building at the corner of Market and High Streets, as well as Greystone Hall, a mansion on a 1000-acre estate along Phoenixville Pike northeast of town.

Growing better mushrooms, however, was arguably not Rettew’s most significant contribution to the scientific community.

By 1900 West Chester was a major manufacturing town, and the Sharples Separator Works was the premier industrial operation in the borough. The HB&T nursery and the HB&D wheel works were based on the industrial organization of farm crafts—growing plants and shaping wood—but the Sharples Separator Company was a "high-tech" operation that combined foundries, machine shops, and metal fabrication with engineering and speculative investment. Oddly enough, it was this powerhouse firm that became the first to declare bankruptcy in the 20th century.

Chester County Mushroom Laboratories Chester County has been a hub of mushroom production since the late 19th century, which Jones traces back to Kennett Square florist William Swayne, who started growing mushrooms in the unused space under the shelves he used to support the carnations in his greenhouses. “The business took off,” writes Jones, “and by the 1920s mushrooms were grown in specialized buildings like those owned by the Edward H. Jacobs Company, the dominant firm in West Chester.” Chemist G. Raymond Rettew found himself inspired to solve the problems facing mushroom production often lamented by his father-in-law, who worked in the industry. Accordingly, Rettew and an investment partner, Joseph Strode,

In 1942, Rettew and his laboratory assistant devised a process for growing penicillin that made mass production possible... “Penicillin production today would not be possible without this method.” When English scientist Alexander Fleming discovered penicillin in 1928, the early production method of growing mold on the surface of liquid in jars was simply too slow to match demand. In 1942, Rettew and his laboratory assistant devised a process for growing penicillin that made mass production possible, and created a subsidiary company named "Fungus Products” for that purpose. “Rettew discovered that adding banana oil to the tanks would separate penicillin from the culture in which it grew,” writes Mark E. Dixon in his article “The Mushroom Man” in the March 2011 issue of Main Line Today. “It was the solution of this problem that finally made possible our winning the race for mass production of penicillin,” reflected Rettew in 1973, as cited in Dixon’s article. “Penicillin production today would not be possible without this method.” Rettew’s game-changing invention incorporated technology from another West Chester company: The centrifuge he used to separate the oil from the penicillin was a cream separator manufactured by Sharples Separator Works. Rettew sold the idea to Reichel Laboratories, which manufactured penicillin used by the military in World War II, where it

was credited with saving tens of thousands of lives. Wyeth Pharmaceuticals acquired Reichel in late 1943 and continued to manufacture vaccines in the West Chester plant until it closed in 2004.

Denney Tag Company Denney Tag Company was the first outside company to move into West Chester, kicking off the borough’s second wave of industrialization, as identified by Jim Jones. Founded in Philadelphia in 1884 by Samuel L. Denney and his brother, they manufactured paper tags used for everything from inventory control to pricing. By the time the company moved from Philadelphia into an old school building on West Barnard Street in the spring of 1888, business was booming, and Denney was the second largest tag manufacturing company in the country. “The firm received a number of enormous contracts, like one for eight million tags in 1890 for the American Express Company, two million in 1894 for a firm in Charleston, South Carolina, and four million in 1900 for a firm in Cincinnati, Ohio,” according to Jones’ research. Business was so good, in fact, that plant superintendent Samuel O. Barber decided to start a company of his own, also located in West Chester, which he named the Keystone Tag Company. World War II government contracts drove Denney’s stock prices through the roof. “In 1948, company treasurer Casper H. Padmore estimated that a single share that cost $20 in 1888 was now worth between $1,850-2,000,” writes Jones, noting that Padmore himself “did well enough to own a silver Rolls Royce.” As Denney continued to expand, they bought up other firms, including Keystone, the Central Tag Company of Chicago, and Reyburn Manufacturing Company, makers of tag-printing machinery, changing their name to Denney-Reyburn in January 1961 to reflect the acquisition. Higher energy costs and tighter OSHA safety regulations chipped away at the company’s profitability starting in the 1970s, leading to a buyout in 1988. The new owners struggled, however, and sold the company two years later to Menasha Company of Wisconsin, who then closed the company down for good a short time later, thus ending West Chester’s tag manufacturing dynasty.

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