The holiday was created on October 1, 1961, when Congress asked the president to designate May 15 to honor peace officers. John F. Kennedy signed the bill into law on October 1, 1962. The Proclamation Signed by President John F. Kennedy:[5]
To pay tribute to the law enforcement officers who have made the ultimate sacrifice for our country and to voice our appreciation for all those who currently serve on the front lines of the battle against crime, the Congress, by a joint resolution approved October 1, 1962 (75 Stat.676), has authorized and requested the President to designate May 15 of each year as “Peace Officers Memorial Day,” and the week in which it falls as “Police Week” and by Public Law 103-322 (36 U.S.C. 175) has requested that the flag be flown at half-staff on Peace Officers’ Memorial Day.
Amended in 1994, Bill Clinton, through Public Law 103-322, directed that the flag of the United States be flown at half-staff on May 15. According to a proclamation by George W. Bush in 2002,
“Peace Officers Memorial Day and Police Week pay tribute to the local, State, and Federal law enforcement officers who serve and protect us with courage and dedication. These observances also remind us of the ongoing need to be vigilant against all forms of crime, especially to acts of extreme violence and terrorism.”
Much of the holiday centers on the National Law Enforcement Officers Memorial wall in Washington, D.C., whose walls feature the names of more than 19,000 law enforcement officers who have been killed in the line of duty.
Source: http://en.wikipedia.org/wiki/Peace_Officers_Memorial_Day