This paper describes a series of linkable individual-level data from late-twentieth century federal in-come tax returns. The full universe Internal Revenue Service (IRS) Form 1040 files from 1969, 1974, 1979, 1984, 1989, and 1994 were held at the Census Bureau since originally being delivered by the IRS shortly after each year’s tax returns were processed. The data were recently made usable for research, and they are now available for request through the Census Bureau’s restricted data research program. This paper discusses the provenance and composition of the files, assesses the coverage and quality of the data, and discussed potential uses of the data for research.