Critical to constructing and interpreting graphs is an individual's understanding of the underlying coordinate systems, yet coordinate systems are often overlooked or taken-for-granted in both mathematics education research and curricula. In this paper, we foreground coordinate systems and present a distinction between two uses of coordinate systems--spatial and quantitative. We describe how attending to this distinction can inform research endeavors and we provide possible alternative interpretations of findings from previous research. We close with implications for the learning and teaching of coordinate systems and graphical representations.