Lock is estimated to be more than 4.5 thousands year old. The earliest locks were made of wood and were discovered in the palace ruins of Nineveh, the capital of ancient Assyria (Persia). The oldest lock discovered were used in the palace’s main gate during reign of King Sargon II. They were similar to wooden cane-tumbler locks in appearance and operation.
Ancient Egyptian Locks were similar to a pin tumbler locks of today. Egyptian locks were made of a large wooden bolt which had slot with several holes on its upper surface. These holes were secured by placing wooden pegs that acted as a key and prevented the bolt from being opened.
According to Schlage history of locks , first metal lock were invented between 870 and 900 by an English craftsmen and the key was invented by Theodore of Samos in the 6th century BC. (Schlage is one of the most popular lock manufacturer founded in 1920 by Walter Schlage in San Francisco)
With the advent of the Industrial Revolution in the late 18th century, most sophisticated locks and keys were manufactured.
In the mid 1770s, lever tumbler lock was invented. The lever tumbler lock used a set of levers to prevent the bolt from moving in the lock. The lever tumbler lock mechanism was perfected by Robert Barron in 1778 and he modified the old lever tumbler lock by introducing double acting lever lock which is still currently used today.
The lever tumbler lock was improved into Chubb Detetctor Lock by Jeremiah Chubb in 1818. A Chubb detector lock was the most advanced and secure tumbler lock of the time. When someone tried to pick the lock or to open it using the wrong key, the lock was designed to jam in a locked state until special regulator key or the original key was used to open.
In 1784, the movable levers lock (invented by Barron and Chubb), was replaced by an alternative method developed by Joseph Bramah. His lock used a cylindrical key that impeded the turning of the bolt into an exact alignment, to open the lock. The lock was said to be unpickable at that time. Bramah started the Bramah Locks company and organized a competition challenging to pick or open his lock for a reward of £200. The challenge remained untouched for over 67 years until, in 1851 at the Great Exhibition, the American locksmith Alfred Charles Hobbs was able to open the lock after some 51 hours.
In 1805, double-acting pin tumbler lock was invented and patented by American physician Abraham O. Stansbury of England. The modern version of the same lock, which is still in use today, was invented by American Linus Yale, Sr. in 1848. Few years later, Linus Yale, Jr. made some serious modification in the old design of pin-tumbler lock and invented smaller flat key with serrated edges within the lock itself. The same modified pin-tumbler lock remains in commercial use today.