Matthieu became involved in the 1837–1838 armed rebellion against British rule in Canada, for which he was forced to flee his native Quebec for safety in the United States, where he worked as a carpenter and a fur trader.

Matthieu was among those who attended the Champoeg Meetings of May 1843, which voted to establish a Provisional Government of Oregon with a view to eventually joining the United States.

In his 90s, Matthieu returned to the public eye as an icon of Oregon's pioneer history, not only for his pivotal vote in 1843 but as the last surviving participant of the 102 men who attended the 1843 Champoeg Meetings.

[2] In 1835 Matthieu became involved with the Société des Fils de la Liberté (Society of the Sons of Liberty), a paramilitary organization which waged an uprising remembered to history as Papineau's Rebellion against British rule.

[5] Matthieu's participation was discovered and the youth was forced to flee Canada for refuge in the United States,[4] crossing the border there by means of a forged passport.

[8] Matthieu came to the Oregon Country with the Elijah White party September 25, 1842, spending his first winter with fellow pioneer Étienne Lucier and discussing politics and government.

[4] As tension over the standoff mounted, Matthieu was one of two individuals to break ranks with backers of British rule, voting instead for formation of an independent Provisional Government of Oregon.

In actuality, the boundaries of American and British control in the Pacific Northwest were determined through international diplomacy, culminating with the Oregon Treaty of 1846, the results of which had nothing to do with popular voting of residents or the existence or non-existence of a provisional territorial government.

[12] Matthieu settled on French Prairie and owned a general merchandising business in Butteville, a small town which he founded located in rural Marion County.

[8] He also schemed on making use of Native Americans as mineworkers, but scurvy and diarrhea led to massive deaths among the first party accompanying him to California and the plan fell to nothing.