History of Flag Day
As the legend goes, it was George Washington and two other members of the Continental Congress who asked Betsy Ross to sew the first American flag sometime in the late spring of 1776. The young widow was only in her early 20's when she completed the first flag with thirteen stars arranged in a circle.
A year later, the Continental Congress officially adopted the design for the national flag, and henceforward the Stars and Stripes symbolized the U.S. around the world.
The first "official" Flag Day was celebrated in 1877 - the flag's centennial. In 1916, a grass roots movement resulted in President Woodrow Wilson issuing a proclamation that called for a nationwide observance of Flag Day on June 14. Although still not an official holiday, Flag Day was made a permanent observance in America in 1949 by Congress who resolved "That the 14th day of June of each year is hereby designated as Flag Day."
Facts of Flag Day
Why red, white and blue? To the original members of the Continental Congress, red stood for hardiness and courage, white for purity and innocence, and blue for vigilance and justice.
Why thirteen stars and stripes? They represented the thirteen American colonies which rallied around the new flag in their fight against the British for self-governance.
The thirteen colonies included Connecticut, Delaware, Georgia, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, South Carolina, Pennsylvania, Rhode Island and Virginia.
To this day, thirteen stripes still commemorate the original colonies. Instead of thirteen stars, today the number of stars on the US flag has grown to 50, representing every state in the Union.
Information from here