Final answer:
Dr. King alludes to the Emancipation Proclamation to emphasize that a century later, the goals of equality it represented had still not been achieved, reinforcing the importance of the civil rights movement.
Step-by-step explanation:
Dr. Martin Luther King Jr., in his iconic "I Have a Dream" speech, alludes to the Emancipation Proclamation to highlight the historical importance of the document and underscore the persistent issue of racial inequality even after a century. King points out that despite the proclamation, which was a significant step towards ending slavery and was meant to be a beacon of hope, the promise of freedom had not yet been fully realized for African Americans. This allusion serves as a powerful reminder to his audience of the long struggle for civil rights and emphasizes the need for continued action towards equality.