Cen A, 4 Megaparsecs distant, is by far the nearest giant elliptical galaxy that we can study in detail. We have used Hubble Space Telescope WFPC2 imaging to obtain deep photometry of its old-halo red giant stars in three different halo and bulge locations, and have used these to construct the metallicity distribution function (MDF) of the stars. This is the only giant E galaxy for which we know a star-by-star MDF without resorting to indirect arguments based on integrated light. I will discuss how the MDF relates to understanding the early evolutionary history of this keystone galaxy.