What I can find is a wikimedia entry with the image but no attribution except the "US Census" and no actual link to any publication put out by the Census Bureau. The archive link goes to a page that does not actually contain this graphic, or the data necessary to generate it, making it a bit suspect to begin with.
The census also don't systematically collect IQ scores or themselves administer IQ tests, making the details, data, and methodology of any study they produce paramount to interpreting this barebones graph. The title of the graph itself is borderline ridiculous, awkwardly stated at best and downright deceptive:
IQ tests are not a requirement for graduating college, and taking them at all is relatively uncommon these days.
As it stands, this image is worthless without context, and that context is oddly elusive except for an anonymous wikimedia post that did not cite the source with any specificity required to authenticate it.