A modular display system having individual stackable electronic display panels of convenient and portable size and mounting structures for the support thereof where the stackable electronic display panels mutually juxtapose, mate, and robustly and mutually and adjustably secure together by the use of connector plates at the top of stackable electronic display panels interfacing with interlocking lower connector assemblies and lower connector plate receptors at the bottom of an overhead vertically situated stackable electronic display panel and by interfacing of latches and cams of latch keeper assemblies at the sides of horizontally situated stackable electronic display panels to form a large electronic sign display. Spring-loaded slide pin assemblies foster rapid and secure connection between vertically situated stackable electronic display panels. Adjustment features are also incorporated to align each stackable electronic display panel.