While cow's milk and plant-based milk are often hypothesized to be substitutes, much remains unknown about the impacts that plant-based milks have on the retail price for cow's milk, if any. We explore the individual retail price relationship between two plant-based milks, almond and soy, with cow's milk. If the markets are cointegrated, and shocks in the plant-based markets affect the cow's milk market, it can add volatility to cow's milk prices, which could have implications for costs and benefits of the USDA Dairy Margin Coverage Program and price calculations by the Federal Milk Marketing Orders (FMMO). However, while we find evidence that plant-based milk prices react to shocks in cow's milk prices, we do not find evidence that cow's milk prices respond to changes in plant-based milk prices.