Flag Day is celebrated on June 14 and honors the adoption of the flag of the United States. However, it's not a federal holiday. In 1916, President Woodrow Wilson issued a proclamation that established June 14 as the date. In 1949, National Flag Day was established by an Act of Congress. The first American flag was introduced on June 14, 1777 by the Continental Congress. No one really knows exactly who designed the first stars and stripes flag or who produced the flag itself.