It's not his rookie card but his 1939 Play Ball is the first full-sized image of Joe DiMaggio to appear in a  major baseball card set.  1939 Play Balls, issued by Gum, Inc. (which would become Bowman Gum after World War 2) are a very underrated series, featuring fantastic and bright black-and-white photos, with no front artwork getting in the way.  The set was released at a time when high quality photographic reproduction was finally supplanting illustration and also the poorer efforts of the craft in prior years.  This PSA 4 of the Yankee Clipper shows just how attractive this set is in both execution and presentation.

The image is undisturbed save for a small remnant dot above and to the right of the "New York" team name on his uniform. Centering is up and to the left and three corners are showing just the tiniest of touches.  The bottom right corner area (but not the corner itself, which is sharp) has sustained a scuff, which is defining the grade but is contained in the border area and is, frankly, not very distracting. The reverse features the "all caps" version of DiMaggio's name and is in remarkable condition.