According to the USPTO, three US patents have issued referencing Juneteenth: 11803924, 11281738, and 8136962 (Google Patents is only aware of the ‘962 patent — good lesson to search both databases). There are some pending applications on mentioning Juneteenth, so there will likely be more in the future.

A seemingly more significant event is the Emancipation Proclamation, from which Juneteenth derives. According to the USPTO the Emancipation Proclamation is referenced in 24 US patents Google Patents is only aware of 23 patents, but identifies one much older patent (before USPTO full text searching), and two fewer recent patents indicating a lag in Google Patents data uploading, again a good lesson to search both databases).

US Patent No. D21862 is the earlier patent identified by Google Patents, and it covers a memorial shield:

The shield is interesting for its revelation of the historic events and persons of significance in 1892:

The large medallions on the shield depict, “Landing of Columbus,” “Landing of the Pilgrims,” “Battle of Lake Erie,” “Washington Crossing the Delaware,”Declaration of Independence,”“Battle of Churubusco,” “Emancipation Proclamation,” and an allegorical design of industrial progress. The smaller medallions depict George Washington, Benjamin Franklin, Abraham Lincoln, James A. Garfield, Ulysses Grant, Thomas Jefferson, H. Wadsworth Longfellow, and Sam. F. B. Morse. Some of these events and persons would likely still be listed today, but with the march of time comes a continual reassessment of what (and who) is important. The Emancipation Proclamation, and its echo Juneteenth, still make the list.