This thesis highlights the problems with relying exclusively on English written versions of treaty to understand the formation of Upper Canada. An analysis of colonial correspondence from the 1790s and Mississauga petitions from the 1790s to the 1840s reveal gaps in the treaty record. By looking beyond treaty texts to include other documents about Crown-Indigenous relations, I reveal that Mississauga fisheries and waterways were never surrendered through the Upper Canadian treaties. The examples of the Toronto (1805) and Head of the Lake Purchases (1806) demonstrate that the English written versions of treaty stand as outliers to the rest of the historical record regarding cessions and surrenders. Indeed, the Mississauga advocated and petitioned for decades about settler encroachment. While Mississauga advocacy evolved over time, the core arguments of Mississauga leaders remained the same: the Mississauga did not cede everything to the Crown.