William Morton is associated with the use of ether as a dental and surgical anaesthetic. He studied at the world's first dental school, Baltimore College of Dental Surgery, but left without finishing his degree. In 1844 he became a student at Harvard Medical School, but again did not finish his studies. However, at Harvard he attended the lectures of Professor Charles Jackson, who in 1844 demonstrated that inhaling ether caused unconsciousness.

Having seen his former business partner Horace Wells fail to convince the medical establishment of the usefulness of nitrous oxide, Morton decided to investigate ether.

Morton administered ether for a surgical operation at Massachusetts General Hospital on October 16, 1846, and the patient felt no pain. He subsequently came to be seen by many as the 'inventor' of anaesthesia although he was not the first person to use ether for surgical anesthesia. Dr. Crawford Williamson Long first used ether as an anesthetic during surgery on March 30, 1842.

Morton attempted to patent the substance he used as an anesthetic as 'Letheon'. However, the “letheon” was quickly shown to be ether, and it was soon after being used in both the United States and Europe.

In 1852 Morton was granted an honorary doctorate by the Washington University in Baltimore. Morton received a patent for ether in the US, which was later revoked, and never received any royalties. He spent his declining years in an attempt to persuade Congress to provide him compensation for his discovery, but this never arrived.

Morton died in 1868 at the age of 48.