Juneteenth National Independence Day is a holiday that celebrates the ending of slavery in the United States. The first Juneteenth celebration took place in Texas in 1866.
That celebration was only one year after June 19, 1865, when Major General Gordon Granger ordered the final enforcement of the Emancipation Proclamation while in Texas.
Celebrating freedom, especially from slavery (which has oppressed and continues to oppress people across the world), is as worthy a cause of celebration than any other.