Amphetamines were first introduced to the market to treat asthma and nasal congestion in the United States. As recognition of the drug’s effects on vigilance became better understood, amphetamines and methamphetamines were used by militaries, most notably during World War II. In the 1950s, amphetamines became popular as weight-loss drugs. Since then, amphetamines have been used as a drug of abuse. The United States designated amphetamines a controlled substance in 1971, under the Controlled Substances Act.