Irwin & Leighton was founded in 1909. The company maintained its headquarters in downtown Philadelphia until 1974 when it moved its operations to King of Prussia, Pa. Irwin & Leightons stock is held exclusively by its employees. Stockholders include corporate officers, project managers, estimators, superintendents, accountants and secretaries. Irwin & Leighton provides a variety construction services. The companys mission is to continue in business by fostering long-term professional relationships, meeting and exceeding the requirements of customers and by employing and challenging skilled professionals to promote company and individual growth. The company provides construction management, pre-construction services, construction services, general contracting, design build, turnkey projects and consulting. Headquartered in King of Prussia, Irwin & Leighton is a privately owned company that employs nearly 100 people.