CLEVELAND — Sonnhalter announced the passing of its founder, C. John Sonnhalter, who died at age 77 after building one of the marketing industry's first agencies dedicated to serving the construction, industrial, and maintenance, repair, and operations (MRO) markets.

John Sonnhalter founded the Cleveland-based agency in 1976 with a focus on helping manufacturers communicate more effectively with skilled trades professionals who specify, recommend, and install their products.

During his nearly four decades leading the firm, Sonnhalter helped develop the concept of business-to-trades (B2T) marketing, which emphasizes reaching professional tradespeople throughout the purchasing process. That approach became a defining strategy for manufacturers serving construction and industrial markets.

Leadership of the agency transitioned to his son, Matt Sonnhalter, beginning in 2003. Matt became president in 2008, and the ownership transition was completed in 2015. John Sonnhalter continued serving as a consultant, mentor, and business development advisor after stepping away from ownership.

According to Sonnhalter, John also authored articles on industrial marketing, created the company's Tradespeople Insights blog, and served as a certified SCORE mentor, advising entrepreneurs and nonprofit organizations. He also helped launch and served on the board of Good Knights of Lorain County LLC.

“My dad taught me that great marketing starts with listening,” said Matt Sonnhalter, president and owner of Sonnhalter. “He respected the men and women who build, repair and maintain our world, and he built an agency that respected them too. His legacy lives on not only through our company, but through the countless clients, colleagues and friends whose lives he touched.”