I confess that I never heard of Juneteenth until I moved to Texas. Even then, it took years before I realized it was an actual historical event, not just a fun portmanteau. To learn more about Juneteenth, which is now a Federal holiday, you can read this article from Learning for Justice. Another good resource is this article from The Kid Should See This about the Google Doodle for Juneteenth, which includes a video and narration by LeVar Burton. For a teaching resource (if you happen to be in school still, or want to bookmark it for next school year) this page from PBS has good discussion questions and video links while also bringing up the reasons some anti-racists may not be in favor of Juneteenth as a national holiday. For information about the symbolism of the Juneteenth flag, pictured below, see this page.
This resource will be added to my Anti-Racist Wakelet. You can currently find more than 45 other resources at that link.