Elizabeth II became Queen February 6, 1952 on the day her father, King George VI, died.
The King's Troop Royal Horse Artillery's six World War I era 13-pounder guns were drawn by 36 horses, which galloped down the park, halted, unhooked and then each gun fired a blank cartridge at 10 second intervals from the stroke of noon.
"This is always a proud moment; we always strive to give as good an account of ourselves as possible and I think the soldiers and horses have done incredibly well today," said Major Mark Edward, commanding officer of the King's Troop Royal Horse Artillery which fired the salute in Hyde Park.
Elizabeth II became Queen February 6, 1952
Edward said the ceremonial aspect of his unit was important but they were also serving soldiers.
"All members of the King's Troop are soldiers first and foremost. They do exactly the same military training as everyone else, and although we do not deploy as a formed unit we have individuals deploying on operations all over the world," he said.
A gun salute was also fired at the Tower of London. While a royal salute normally comprises 21 guns, this is increased to 41 if fired from a royal park or residence.
The Tower of London fires a unique salute of 62 guns because it is a royal residence and it also includes an additional 21 guns for the citizens of the city of London to show their loyalty. Gun salutes of 21 guns were also fired in York and Edinburgh.