The recent growth in digital technologies are enabling cities to undergo transformations for streamlining smart services and offering new products. Digitization has changed the way citizens and stakeholders live, work, collaborate, and communicate. This disruptive change interconnects with all information systems and processes that are important for providing services. Although, digital transformation present opportunities for achieving smart cities. Municipalities still struggle with managing data integration and complexity. Accordingly, this study systematically reviews 70 research articles from 1999 to 2020 and discusses on development and state-of-the-art of Enterprise Architecture (EA) and digital transformation of cities into smart cities.