The South Korea–United States alliance began as a security arrangement, but over the years has grown to be an important economic relationship. In the 1950s, South Korea was a poor country, but by the 1960s the ROK economy was on its way to becoming the “Miracle on the Han River.” Over the years, trade ties have grown significantly along with foreign direct investment. An important element of economic ties is the KORUS FTA that went into effect in 2012. South Korea has increased its trade in goods while the United States has seen an increase in ROK investment and the provision of services. However, the Trump administration has been unhappy with the growing trade deficit and has called for a renegotiation of the FTA. This chapter examines the economic elements of the relationship as an important indicator of the evolution of the alliance.