Mason & Hanger
Design ServicesKentucky, United States201-500 Employees
Mason & Hanger provides architectural and engineering design services for facilities that require stringent security and mission-specific requirements, serving government clients globally. As part of the Day & Zimmermann family, it has served the U.S. government for nearly two centuries, working with agencies such as the Department of Defense, Homeland Security, State, Energy, and the Intelligence Community. Headquartered in Lexington, Kentucky, the firm identifies itself as the oldest operating A/E practice in the United States, with a history spanning almost 200 years and projects delivered across many states and countries. The company operates from several U.S. offices, including Lexington and locations in Huntsville, Alabama; Chantilly, Virginia; Glen Allen, Virginia; and Virginia Beach. Recent developments include national recognition at the ACEC Engineering Excellence Awards in 2026 for the New Consulate Compound in Nogales, Mexico, reflecting ongoing achievement in complex, secure design.