viii, 122 p. / This thesis examines the intersection of republicanism and imperialism in the early nineteenth-century Americas. I focus primarily on Joel Roberts Poinsett, a United States ambassador and statesman, whose career provides a lens into the tensions inherent in a yeoman republic reliant on territorial expansion, yet predicated on the inclusive principles of liberty and virtue. During his diplomatic service in Chile in the 1810s and Mexico in the 1820s, I argue that Poinsett distinguished the character of the United States from that of European empires by actively fostering republican culture and institutions, while also pursuing an increasingly aggressive program of national self-interest. The imperial nature of Poinsett's ideology became pronounced as he pursued the annexation of Texas and the removal of the Cherokee Indians, requiring him to construct an exclusionary and racialized understanding of American republicanism. / Adviser: Carlos Aguirre