This chapter examines the emergence of Populist organizing in southern Dakota Territory, focusing in particular on the origins of the Farmers’ Alliance. It begins by discussing the organizational ecology surrounding the Dakota Alliance movement. Held together by a shifting cadre of movement entrepreneurs, the Populist movement in the Dakota Territory included not only local Alliance organizations, but the newspapers with which they partnered, and the cooperative business ventures that they spawned. The remainder of the chapter examines local Alliance activity in the East River region of southern Dakota. It provides an in-depth look at life in a local Alliance, as well as a statistical analysis of the correlates of Alliance activity, including market building. Following the contours of the railroad network, the Alliance thrived in middling townships that were no longer part of the frontier, but had yet to emerge as central locales.