Multiple modality is spread across the wider Atlantic region, both within individual varieties and across variety types. Based on corpus-based evidence, it is argued that first and second tiers of multiple modals carry high diagnostic value and that regionally separated Anglophone areas differ in their preference for first- and second-tier components in modal constructions. Semantics is a diagnostic typologically as there exists a continuum, the “Multiple Modal Belt,” which consists of three main clusters that are primarily differentiated by their respective compositional preferences: North American varieties favor epistemic ‘weak probability’ elements (~might) as first-tier modals, Caribbean varieties ‘high probability’ or ‘certainty’ (~must). Multiple causation and contact-induced change are offered as explanations for supra- and sub-regional variation in the Atlantic region, and there is strong evidence that the preference for second-tier components originally represented Scottish origin and subsequent diffusion with locally differing contact scenarios. Locally distinct preferences for semantic compositionality – particularly based on preference for first-tier ‘high-probability’ modals – are used to model a geo-typological clustering of varieties throughout the wider Atlantic region.