In this thesis, we examine the relationship between the equilibrium prices of spatially separated market participants and the transportation network that connects them; we focus in particular on isolating the effect that the transportation network can have on price integration. We first find that certain network structures and link costs can guarantee a bound on price differences between spatially separated participants when there are no capacity constraints. We extend this analysis to the case when there are binding transportation constraints, and generalize the effects of the transportation network on price integration using a time series decomposition. We then develop an empirical methodology, termed the submarket detection method (SDM), which can be used to infer when binding transportation constraints exist by analyzing regional pricing data from a competitive market, and conclude by using the SDM in a case study of the US gasoline market.