Anesthesia dates back to the mid-1800s. Before the discovery of anesthesia over a century ago, few surgeries could be performed. Even a condition like appendicitis, which by current standards is easily treated, was usually fatal.
What eventually evolved into anesthesia as we know it today was ushered in with the chance observation that the inhalation of nitrous oxide ("laughing gas") produced a state of intoxication during which people became highly amused and insensitive to pain.
In 1842, Dr. Crawford Long of Georgia used ether to perform the first painless surgery. Dr. Horace Wells demonstrated painless dentistry under nitrous oxide in 1844. In 1846, Dr. William Morton astonished doctors at Massachusetts General Hospital when he achieved anesthesia with ether.
The new science of anesthesiology began to spread around the world. After World War II ended in 1945, major developments in the field of anesthesiology opened new avenues of medical and surgical care that were previously unthinkable.
Thus began the modern era of anesthesia, which has advanced enormously, especially in the last two decades.