The most often cited and used list of America's legal executions is one created based on the research of amateur historian M. Watt Espy, Jr. His collection has been used in various forms, including an initial list of executions under State authority; the Espy File, a computerized list available from the Inter-university Consortium for Political and Social Research [ICPSR] of about three fourths of the estimated number of executions; an ICPSR Supplement of most of the remainder known to Espy; and the collection itself, documenting in some form each of the executions. Although the Espy File and collection have been widely praised, there are serious problems in the ICPSR version of the Espy File and additional limitations with the collection itself. Researchers should be cautious in relying upon the Espy File for quantitative analyses or even as a complete source of basic information on the record of American executions from the first temporary and permanent colonization of what is now the United States to the 20th century. (Published Abstract)