This chapter explores the purpose and future of the Quadrilateral Security Dialogue (“the Quad”) from the perspective of the United States. It is argued that the Quad has the potential to serve US’ interests by institutionalising the idea of America belonging to a single Indo-Pacific megaregion that encompasses the Indian Ocean and Western Pacific maritime zones. This is something that the United States wants to promote with a view to building a broad international coalition to blunt the growth of Chinese influence along the maritime rim of South and East Asia. However, the durability of the Indo-Pacific construct will depend, in part, upon the degree of institutionalisation that can be achieved via the Quad and its adjunct (“Quad Plus”) relationships. The chapter concludes that there are some powerful reasons to doubt whether the Quad will be enough to sustain the imagination of shared security interests over the long haul.