When William Seibel started the business in 1944, he was already an industrial arts teacher at Lancaster High School. His first business venture was making children’s tin pail and shovel sets. Shortly thereafter William expanded upon the business by hiring a welder and setting him up in his garage.

The business soon expanded past the limitations of William’s garage. Land was purchased in Lancaster at 38 Palmer Place. After numerous expansions the address still stands as the home of Seibel Modern Mfg. The firm’s first big break occurred when Gould National Battery (GNB), a business at the time located in nearby Depew contracted Seibel to manufacture steel cases for industrial batteries.

Meanwhile William’s two sons; Leon, also known as Lee and Roger had grown up and gone to college. Lee attended the Rensselaer Polytechnic Institute to study civil engineering, later attending Purdue to earn his masters in construction management. Roger embarked on a different path through medical school. Upon his death in 2007, the ECMC Burn Treatment Center was renamed the "Roger W. Seibel, MD, Burn Treatment Center" in his honor.

In 1970, Lee joined his father in the business after working for Tri-Delta Construction for five years following graduation. During the first 10 years of Lee’s employment, Seibel Modern Mfg. went through 7 additions and expanded into many new manufacturing endeavors. His leadership role continues on a daily basis handling the company's large projects while overseeing the daily operation of the corporation.

Mark, a graduate of Clarkson University is now the third generation to lead Seibel. He is in charge of the firm’s battery division. As vice president he is important to the continued growth of the company. Through repeat successes in the construction industry Seibel has earned work from clients such as general contractors, concrete precastors and well known names such as: Kiska Construction, American Bridge, VStructural LLC, Lehigh Construction and Yonkers Construction.