On Saturday, millions of people across America, including right here in Boston, will celebrate Juneteenth, first celebrated on June 19th, 1865. 156 years ago, the enslaved people in Texas found out they were free — two years after the Emancipation Proclamation. The event, which first had the most meaning for the people of Texas, has now become an observance that recognizes the history but also embraces the broader issue of the meaning of freedom today. Nearly every state in the country now recognizes the holiday, and this year, many employers gave staffers the day off.