This paper attempts to quantify the sports industry and the economic activity it supports in the United States. Since national output is measured by Gross Domestic Product (GDP), the output of the national sports industry should be measured by Gross Domestic Sports Product (GDSP), which is calculated using the rules and methodology put forth by the U.S. Department of Commerce. Using that estimate, the amount of economic activity supported by the sports industry is calculated using an input/output model of the national economy. The result of this analysis is that the size of the sports industry was $152 billion in 1995, and supported an additional $259 billion in economic activity.