According to the U.S. Department of Veterans Affairs, this was the resolution adopted by the Continental Congress on June 14, 1777, following the report of a special committee that had been assigned to suggest the flag’s design. Schools all over the country began holding Flag Day celebrations in the late 1800s, but it wasn’t until 1916 when President Wilson issued a proclamation asking for June 14 to be observed as the National Flag Day. On August 3, 1949, Congress approved the national observance, and President Harry Truman signed it into law.
You can find many instances of Flag Day celebrations in Wyoming Newspapers dating back to the 1800s — search for “Flag Day” in quotes to find a bunch.
A headline in the June 9, 1943 Slip Stream, the official paper of the Army Air Base in Casper, proclaimed: “Air Base Will Take Part in Flag Day Parade.” The event was sponsored by the Casper Elks club with assistance from Air Base personnel. Businesses planned to close for the parade, which was “expected to be one of the largest ever held in Casper and hundreds of Air Base troops will participate. Scheduled to take part are the Air Base color guards, and many other units.”