What happens to an imperial economy after empire? How do economics, security, and ideology interact at the new state frontiers? Does trade always break down ideological barriers? The eastern borders of Poland, Latvia, and Estonia comprised much of the interwar Soviet state’s western frontier – the focus of Moscow’s revolutionary aspirations and security concerns. These young nations paid for their independence with the loss of the Imperial Russian market. Łódź, the “Polish Manchester,” had fashioned its textiles for Russian and Ukrainian consumers; Riga had been the Empire’s busiest commercial port; Tallinn had been one of the busiest – and Russians drank nine-tenths of the potato vodka distilled on Estonian estates. Eager to reclaim their traditional market, but stymied by the Soviet state monopoly on foreign trade and impatient with the slow grind of trade talks, these countries’ businessmen turned to the porous Soviet frontier. The dissertation reveals how, despite considerable misgivings, their governments actively abetted this traffic. The Polish and Baltic struggles to balance the heady profits of the “border trade” against a host of security concerns shaped everyday lives and government decisions on both sides of the Soviet frontier. Drawing on government archives, business records, and periodicals from seven countries, the dissertation uncovers the changing composition and scale of these “semi-contraband” (and fully-contraband) flows that Soviet authorities struggled to stem. It reveals the centrality of cross-border Jewish networks to this trade, and the implications of this centrality for Polish and Latvian Jews. It traces (and maps) the proliferation of hundreds of government-sanctioned “barter stations” along Poland’s, Latvia’s, and Estonia’s Soviet frontiers, and profiles their operators and visitors. While these bustling shops supplied smugglers with goods, they supplied the Bolsheviks with a tangible, everyday manifestation of hostile capitalist encirclement. In the end, the dissertation suggests that by linking Soviet consumers with the outside world against Moscow’s wishes, the ports and distilleries of Riga, Tallinn, and Tartu and the cloth factories of Łódź inadvertently fashioned the foundations of the interwar Iron Curtain.