Patrick Anthony McCarran was born in Reno, Nevada, on August 8, 1876. He graduated from the University of Nevada in 1901 and was elected to the Nevada legislature in 1903. A champion of the working man, he sponsored the country's first law limiting the working day to eight hours. While working as a sheep herder he studied law, and in 1905 he was admitted to the bar. He practiced law in Tonopah and Goldfield. He was district attorney in Nye County, Nevada, from 1907 to 1909 and established a law practice in Reno in 1909; he served as an associate justice of the Supreme Court of Nevada from 1913 to 1917 and was its chief justice from 1917 to 1919. His opinions on fingerprinting and property rights are considered landmarks. In 1919 McCarran returned to private practice.

Elected to the U.S. Senate in 1932, he served until his death. He led the fight to prohibit President Roosevelt from packing the Supreme Court and to curb presidential treaty-making powers. He sponsored laws concerned with the nation's security, including the Civil Aeronautics Act of 1938; the Federal Airport Act of 1945; the Administrative Procedures Act of 1946; the McCarran-Woods Act of 1950, which required registration of communists and their exclusion from government; and the McCarran-Walter Act of 1952, which tightened the immigration laws. He was also an early advocate of a separate U.S. Air Force.

McCarran died in Hawthorne, Nevada, on September 28, 1954.