This dissertation presents the first full grammatical description of unprompted (spontaneous) speech in pidgin Chinook Jargon [synonyms Chinúk Wawa, Chinook]. The data come from a dialect I term ‘Kamloops Chinúk Wawa’, used in southern interior British Columbia circa 1900. I also present the first historical study and structural analysis of the shorthand-based ‘Chinuk pipa’ alphabet in which Kamloops Chinúk Wawa was written, primarily by Salish people. This study is made possible by the discovery of several hundred such texts, which I have transliterated and analyzed. The Basic Linguistic Theory-inspired (cf. Dixon 2010a,b) framework used here interprets Kamloops Chinúk Wawa as surprisingly ramified in morphological and syntactic structure, a finding in line with recent studies reexamining the status of pidgins by Bakker (e.g. 2003a,b, forthcoming) among others. Among the major findings: an unusually successful pidgin literacy including a widely circulated newspaper Kamloops Wawa, and language planning by the missionary J.M.R. Le Jeune, O.M.I. He planned both for the use of Kamloops Chinúk Wawa and this alphabet, and for their replacement by English. Additional sociolinguistic factors determining how Chinuk pipa was written included Salish preferences for learning to write by whole-word units (rather than letter by letter), and toward informal intra-community teaching of this first group literacy. In addition to compounding and conversion of lexical roots, Kamloops Chinúk Wawa morphology exploited three types of preposed grammatical morphemes—affixes, clitics, and particles. Virtually all are homonymous with and grammaticalized from demonstrably lexical morphs. Newly identified categories include ‘out-of-control’ transitivity marking and discourse markers including ‘admirative’ and ‘inferred’. Contrary to previous claims about Chinook Jargon (cf. Vrzic 1999), no overt passive voice exists in Kamloops Chinúk Wawa (nor probably in pan-Chinook Jargon), but a previously unknown ‘passivization strategy’ of implied agent demotion is brought to light. A realis-irrealis modality distinction is reflected at several scopal levels: phrase, clause and sentence. Functional differences are observed between irrealis clauses before and after main clauses. Polar questions are restricted to subordinate clauses, while alternative questions are formed by simple juxtaposition of irrealis clauses. Main-clause interrogatives are limited to content-question forms, optionally with irrealis marking. Positive imperatives are normally signaled by a mood particle on a realis clause, negative ones by a negative particle. Aspect is marked in a three-part ingressive-imperfective-completive system, with a marginal fourth ‘conative’. One negative operator has characteristically clausal, and another phrasal, scope. One copula is newly attested. Degree marking is largely confined to ‘predicative’ adjectives (copula complements). Several novel features of pronoun usage possibly reflect Salish L1 grammatical habits: a consistent animacy distinction occurs in third-person pronouns, where pan-Chinook Jargon 'iaka' (animate singular) and 'klaska' (animate plural) contrast with a null inanimate object/patient; this null and 'iaka' are non-specified for number; in intransitives, double exponence (repetition) of pronominal subjects is common; and pan-Chinook Jargon 'klaksta' (originally ‘who?’) and 'klaska' (originally ‘they’) vary freely with each other. Certain etymologically content-question forms are used also as determiners. Kamloops Chinúk Wawa’s numeral system is unusually regular and small for a pidgin; numerals are also used ordinally in a distinctly Chinook Jargon type of personal name. There is a null allomorph of the preposition 'kopa'. This preposition has additionally a realis complementizer function (with nominalized predicates) distinct from irrealis 'pus' (with verbal ones). Conjunction 'pi' also has a function in a syntactic focus-increasing and -reducing system. / Graduate