Vermont is the first and only state in the US to establish mandatory labels for food containing genetically modified organisms (GMOs). This thesis investigates the impact of the mandatory labeling law as it relates to changes in prices, quantities sold, and opinions of GMOs. First, grocery store scanner data from Vermont and Oregon are compared using triple difference (difference-in-difference-in-difference) models. Next, Vermont, Oregon, and Colorado survey response data are compared using difference-in-difference models. The findings reveal that there is a general price premium for non-GMO goods of $0.05/oz across all states and times, that mandatory labeling laws do not result in a short-term change in quantities sold or prices of GMO products, and that both mandatory labeling laws and failed mandatory labeling referendums cause an increase in support for GMOs in the food supply. The implications of this research are that mandatory GMO labels did not impact short-term prices or sales and increased the level of support for GMOs.