Do not make plans to mail your sweetheart a love letter on Thursday, June 19, because, due to the federal holiday Juneteenth, the U.S. Postal Service will not be open to accept your correspondence. So, what is Juneteenth?For generations, many Americans have celebrated June 19 as the day in 1865 when the last enslaved people, predominately black, in the U.S. learned they were free. Report...