Across the last century, the condition known as intellectual disability (ID) has been labeled by assorted terms, its key features have varied, and recommendations for its identification have been divided. In light of recent changes to the diagnostic criteria for ID and to federal legislation, this study was designed to compile and summarize information about the state special education criteria for this condition and its associated assessment process, as they guide school-based and associated practices. Authors independently double-coded components of all ID regulations and guidelines from the 50 United States and the District of Columbia in pairs, which was then checked and corrected for inconsistencies. A total of 10% of states provided only the federal definition of ID. Intellectual disability was the most common term used across states, but it was used by only 63% of them. To meet the intellectual deficit criterion, 37% of states referenced a fixed IQ cutoff, and 49% referred to a flexible IQ cutoff. In contrast, most states did not refer to what score types or criteria should be referenced when identifying adaptive behavior deficits. The influence of the recently updated diagnostic criteria for ID and federal legislation was evident, as several patterns of changes were apparent since the last studies of this type. The assessment in intellectual functioning was more well defined than the assessment of adaptive behavior. Health-related features associated with ID were not commonly referenced. These results can inform school psychology practice, training, and related research.