Very few century-old companies keep the same ideals in place through two world wars, globalization, technology and market shifts, and ownership successions – but Day & Zimmermann has managed to do just that.
Founded on a bedrock of excellence, values, hard work, and commitment to its customers and employees, Day & Zimmermann has prospered despite technological upheaval, global conflict, and economic turmoil.
Day & Zimmermann Timeline
The Early Years
The company was founded in 1901 in Philadelphia when Charles Day, a young engineer, joined in a consulting partnership with Kern Dodge. Several years later, John Zimmermann joined the company, bringing with him significant financial capabilities and business relationships.
The Day & Zimmermann of the early twentieth century was at the forefront of a major technological revolution. At the time, efficiency studies and automation were sweeping through America's factories. The young company helped modernize and automate factories, build facilities, and even participate in public utility management.
- 1908: John Zimmermann joins Dodge & Day. During construction of the Panama Canal, Day & Zimmermann establishes a world record for hauling concrete.
- 1914: Day & Zimmermann designs foil wrapping machines for the world famous Hershey's Kisses.
The War Years
Day & Zimmermann built its reputation on the intellectual capital of its founders, but it grew through the steady loyalty and hard work of its employees. When World War I broke out, Charles Day had a young family and a successful business, but he was also a patriot and joined the first wave of infantry volunteers. During the war, he played a distinguished role in the logistics side of the conflict, traveling to Europe several times to help the continent prepare for the massive influx of American soldiers and war material.
The postwar years were kind to Day & Zimmermann. As American industry entered the boom of the 1920s, the company's expertise was regularly called upon. Day & Zimmermann built and remodeled plants for a wide variety of industrial customers.
- 1937: Day & Zimmermann creates one of the world's first supermarket design concepts for Safeway.
- 1940: H.L. Yoh Company is founded as the nation's first temporary technical staffing firm.
- 1941: Day & Zimmermann sets a record by bringing the Iowa Ordinance Plant from design to start-up in eleven months.
The 1960's & Beyond
The true seeds of the modern Day & Zimmermann, however, were sown in 1961, when it was purchased by the H.L. Yoh Company, the nation's first technical staffing firm. Founded by Harold Yoh in 1940, the Yoh Company had provided technical assistance on a variety of projects for companies like Lockheed, Boeing, and NASA.
The new company prospered through the 1960s with a diverse portfolio of engineering and industrial projects. By the time Day & Zimmermann celebrated its sixty-fifth birthday, it had served hundreds of corporate customers all over the world. Day & Zimmermann had developed the first foil-wrapping machines for the famous Hershey's Kisses and established a world record for concrete-hauling during construction of the Panama Canal in the early twentieth century. It had built bridges and factories throughout the country and assisted in billions of dollars worth of public works projects and appraisal activities.
- 1960: Yoh Company begins work on the Mercury project beginning a long-standing relationship with NASA.
- 1961: Day & Zimmermann and Yoh Company merge to create one of the largest technical organizations in the world.
A Business Evolution
Day & Zimmermann's evolution wasn't over. In 1976, the United States' bicentennial year, Spike Yoh bought Day & Zimmermann from his father and brought new energy and focus to the family company. Spike believed in growth through acquisition and diversification. He wanted to expand Day & Zimmermann into new areas to complement the existing capabilities in contract staffing, engineering, construction, and munitions.
- 1973: Day & Zimmermann begins managing more than 300 firms in multi-year U.S. Postal Service modernization program.
- 1982: Yoh Company staffs a DuPont support office, leading to a major Day & Zimmermann alliance that would continue through the 1990's and beyond.
- 1988: Day & Zimmermann Protection Technology wins its first Department of Energy contract at Idaho National Environmental Engineering Laboratory.
- 1991: Day & Zimmermann Hawthorne Corporation ships 72,000 tons of ordnance to support the Gulf War.
- 1992: Day & Zimmermann completes engineering and construction on an award winning Pepperidge Farm plant in Denver, PA.
A New Millenium
In 1998, after more than twenty years as its leader, Spike Yoh retired from Day & Zimmermann. He was succeeded as CEO by his son Hal Yoh. By this time, in fact, all five of Spike's children were active in Day & Zimmermann management. The transition to the third generation of Yoh leadership was smooth, making Day & Zimmermann one of the few large, successful private corporations (fewer than 15% of private companies accomplish this milestone) in America to have third-generation leadership. That same year, Day & Zimmermann was recognized for its expertise, winning the prestigious National Family Business of the Year award.
- 1999: Day & Zimmermann acquires Mason & Hanger, joining two of the oldest diversified services companies in the U.S.
- 2000: Day & Zimmermann NPS® becomes the largest power maintenance contractor in the U.S.
- 2001: Day & Zimmermann commemorates a Century of Service!
- Today, Day & Zimmermann has changed greatly from the engineering consulting partnership founded a century ago.
Excerpted from The Legend of Day & Zimmermann, by Jeffrey L. Rodengen.

