Acetaminophen (also known as paracetamol) was first synthesized in 1878 by Harmon Northrop Morse. It was initially used to treat pain and fever starting in 1893. However, it did not come into widespread therapeutic use until the early 1950s. The first marketed product in the U.S. was Trigesic in 1950, but it was removed due to safety concerns and then reintroduced in 1952 as a prescription drug. The brand Tylenol, which popularized acetaminophen, was introduced in 1955 by McNeil Laboratories and became available over the counter by the early 1960s.