In this chapter we investigate the relevance of diachronic research to the mapping between form and interpretation in the realization of illocutionary acts, that is, the communicative actions achieved through the production of an utterance. Discussing the complex relation between sentence mood (verb positioning) and verbal mood, as well as the contribution of modal particles to the expression of illocutionary force in a diachronic perspective, we argue for the relevance of a cartographic approach to the layout of the left periphery, by which these diachronic processes can be described in a uniform way and explained in a systematic manner through the syntactic encoding of information pertaining to the interface between utterance and discourse in the highest layer of clause structure. We first present a case study in which illocutionary force is affected by the diachronic process of grammaticalization of an adverbial particle which over time turns into a clause-typing maker; we show that the semantic bleaching of a diverse lexical item is generally linked to the subsequent development of a functional usage along a well-attested diachronic path. We then turn to analyze some instances of finite verb movement into the C-domain that we argue serve to activate Force-related projections; in particular, we argue that the position of the inflected verb can be used to mark the distinction between independent clauses or speech acts and dependent clauses or simple propositions. We discuss evidence in the history of German in which positioning of the finite verb was recruited to indicate clausal dependency that was originally signaled by verbal mood. We finally discuss finite verb movement into the C-domain by examining the distribution of subject clitic inversion in some North-Eastern Italian dialects, arguing that the finite verb can be spelled out in different structural positions in the left-periphery related to different aspects of illocutionary meaning.