National Flag Foundation is the foremost authority on the U. S. Flag in the world.
NFF is The Select Web Guide For Proper Use and Care of the U.S. Flag
"Throughout the history of our nation, the flag has evoked intense, sincere feelings of patriotism." Jimmy Carter, 39th President of the United States
The source of this material is the U.S Flag Code, which was finalized in 1924 and distributed to millions of Americans by various patriotic organizations.
Congress adopted the Code in June of 1942 and has amended it several times since then. The U.S. Code as it relates to the flag is advisory only and has no penalities attached to it at this time.