The article by Richard R. Heim Jr. reviews the development and evolution of drought indices used in the United States over the past century. Drought, a recurring phenomenon affecting various sectors, is defined by the American Meteorological Society into four categories: meteorological, agricultural, hydrological, and socioeconomic. The complexity of drought and its diverse impacts make it challenging to develop a single, universal definition or index. Early drought indices, such as those based on precipitation deficits, were often region-specific and lacked comprehensive consideration of environmental factors. The Palmer Drought Index, introduced in 1965, represented a significant advancement by incorporating antecedent precipitation, moisture supply, and demand into a hydrologic accounting system. However, it has limitations, particularly in semi-arid and dry subhumid climates, and its performance varies across different climate regimes. Post-Palmer indices, such as the Surface Water Supply Index (SWSI) and the Standardized Precipitation Index (SPI), have been developed to address these limitations and provide more robust tools for drought monitoring and assessment. These indices integrate multiple factors, including snowpack, reservoir storage, and precipitation, to better capture the complexity of drought conditions. The article also discusses the use of satellite-based technologies, such as the Vegetation Condition Index (VCI), for real-time drought monitoring and the development of drought atlases to provide spatial and temporal insights into drought events. Overall, the review highlights the ongoing efforts to improve drought indices to better serve various sectors and stakeholders.The article by Richard R. Heim Jr. reviews the development and evolution of drought indices used in the United States over the past century. Drought, a recurring phenomenon affecting various sectors, is defined by the American Meteorological Society into four categories: meteorological, agricultural, hydrological, and socioeconomic. The complexity of drought and its diverse impacts make it challenging to develop a single, universal definition or index. Early drought indices, such as those based on precipitation deficits, were often region-specific and lacked comprehensive consideration of environmental factors. The Palmer Drought Index, introduced in 1965, represented a significant advancement by incorporating antecedent precipitation, moisture supply, and demand into a hydrologic accounting system. However, it has limitations, particularly in semi-arid and dry subhumid climates, and its performance varies across different climate regimes. Post-Palmer indices, such as the Surface Water Supply Index (SWSI) and the Standardized Precipitation Index (SPI), have been developed to address these limitations and provide more robust tools for drought monitoring and assessment. These indices integrate multiple factors, including snowpack, reservoir storage, and precipitation, to better capture the complexity of drought conditions. The article also discusses the use of satellite-based technologies, such as the Vegetation Condition Index (VCI), for real-time drought monitoring and the development of drought atlases to provide spatial and temporal insights into drought events. Overall, the review highlights the ongoing efforts to improve drought indices to better serve various sectors and stakeholders.