(CNN)-Nike is adding June 19, a holiday called Juneteenth, to its list of official, paid company holidays.

The sportswear giant joins a growing number of companies that announced this week they are making Juneteenth, the oldest known US celebration of the end of slavery, an annual company holiday. 

Twitter, Square and Vox Media also plan to do the same. Nike CEO John Donahoe made the announcement in a letter to employees Thursday, along with several other actions the company plans to take in light of nationwide demonstrations calling for racial justice.

The announcements come as President Donald Trump said Thursday he plans to return to the campaign trail on June 19.

Juneteenth honors the day in 1865 on which, more than two years after the Emancipation Proclamation was issued, Union soldiers landed in Galveston, Texas, and announced the news of the proclamation to enslaved African Americans. That coastal area of Texas was the last to hear that the Civil War had ended two months earlier.