Cannon published her first catalog of stellar spectra as part of the Henry Draper Memorial project.
In 1901, Annie Jump Cannon published her first major catalog of stellar spectra in the Annals of the Astronomical Observatory of Harvard College, as part of the ongoing Henry Draper Memorial project funded by Mary Anna Draper in honor of her late husband.
This early catalog documented Cannon's refinements to the spectral classification system, building on the work of Williamina Fleming and Antonia Maury. Cannon simplified and reordered the existing alphabetical classification scheme into the now-famous sequence O, B, A, F, G, K, M — a temperature-based ordering that remains in use by astronomers to this day, memorized by generations of students through the mnemonic "Oh Be A Fine Girl/Guy, Kiss Me."
The publication of this catalog established Cannon as a rising authority in stellar spectroscopy and set the stage for her decades-long effort to classify hundreds of thousands of stars. Her methodical, rapid, and remarkably accurate technique for classifying stellar spectra — she could classify up to three stars per minute by eye — became the gold standard for the field. This early work laid the groundwork for what would eventually become the monumental nine-volume Henry Draper Catalogue, one of the most important reference works in the history of astronomy.