In 1995, the original Healthy Eating Index was developed by the USDA Center for Nutrition Policy and Promotion, in cooperation with the USDA Food and Nutrition Service and the USDA Agricultural Research Service, to measure how well the diets of Americans align with the Dietary Guidelines for Americans. While the main purpose of the HEI has remained the same throughout the series of HEI updates, the design and application of the current HEI have changed substantially since its inception. These new features are reflected beginning with the HEI-2005. Documentation related to the original HEI has been archived. (author abstract)