Cointegration was tested between organic and conventional corn and soybean markets in several locations throughout the U.S. using a unique dataset. Organic prices were found to behave like pure jump processes rather than diffusions. A simple specification for pure jump processes is introduced and used with Monte Carlo methods to compute appropriate critical values for unit‐root and cointegration tests. The findings indicate that no long‐run relationship exists between organic and conventional prices, implying that price determination for organic corn and soybean is independent from that of the conventional crops. This suggests that organic corn and soybean prices are driven by demand and supply forces idiosyncratic to the organic market. For each crop, cointegrating spatial relationships are found between prices at the main organic markets. However, such relationships are generally weaker than the ones for the corresponding conventional prices, implying that organic markets are more affected by idiosyncratic shocks than conventional markets. [JEL Classification: Q130 – Agricultural Markets and Marketing; Cooperatives; Agribusiness Q180 – Agricultural Policy; Food Policy].