U̱t‑Maꞌin (Kainji, Benue-Congo, Niger-Congo), spoken in northwestern Nigeria by at least 40,000 people, has two morpho-syntactically distinct Progressive constructions – the Intransitive Progressive Construction and the Transitive Progressive Construction. In this talk I present (i) the synchronic structure of each construction, (ii) likely historical sources of the distinct morphology, and (iii) a comparison of the U̱t‑Maꞌin Progressive Constructions with cognate elements from four Kainji language clusters. The Predicate Nominal Construction [NP COP NP] is the diachronic source for both U̱t‑Maꞌin Progressive Constructions. The morphological complexity of the U̠t Ma’in noun class system holds the key to understanding the distinct elements of the two Progressive constructions: formal differences between these two constructions are found in the morphological composition of the NP predicate (e.g. the second NP in the Predicate Nominal structure [NP COP NP]). No single source component has grammaticalized to mark progressive aspect in U̱t‑Maꞌin, rather the combination of several morphosyntactic elements came together to create the progressive. Formal changes in several morphosyntactic elements within each of the two Progressive constructions provide evidence that originally nominalized verb forms are gradually becoming less noun-like and more verb-like. These developments are examples of constructionalization as the Progressive Constructions exist as new form-meaning pairs distinct from the Predicate Nominal source (Traugott & Trousdale 2013). These formal changes also show signs of adjustment (Heine and Reh 1994; Heine 1993), whereby a construction moves toward isomorphism, that is, a one-to-one correspondence between form and meaning. Specifically, various stages of morphological loss occur in a gradual wave throughout the lexicon and affect particular lexemes when these are used in Progressive constructions.