John Anton Blatnik was born on August 17, 1911, in Chisholm, Minnesota, to Slovene immigrant parents. He graduated from Winona State Teachers College, now known as Winona State University, and worked as a chemistry teacher in Chisholm.

His political career began in 1940 when he served in the Minnesota State Senate until 1944. During World War II, he volunteered for the United States Army Air Corps and was chief of the Office of Strategic Services' mission with Tito's Yugoslav partisans for almost a year.

In 1946, John Blatnik was elected to Congress representing Minnesota's 8th District, running on the newly unified ticket of the Minnesota Democratic-Farmer-Labor Party. He was re-elected 13 times without much difficulty, serving from January 3, 1947, to December 31, 1974.

During his tenure, he introduced a bill to make Leif Erikson Day a nationwide observance, which was adopted unanimously by Congress in 1964. He was an early supporter of the Saint Lawrence Seaway and helped develop the original legislation to build it.

John Blatnik also voted for the Civil Rights Act of 1964 and served as chairman of the Public Works Committee during his last two terms in Congress. As chairman, he shepherded the Federal Water Pollution Control Act, better known as the Clean Water Act, to passage in 1972.

In 1955, he married Gisela Hager, and they had three children. After his first wife's death, he married Evelyn Castiglioni. John Blatnik died on December 17, 1991, in Forest Heights, Maryland, and was survived by his second wife.

The bridge for Interstate 535 crossing the Superior Bay and the Saint Louis Bay between Wisconsin and Minnesota was renamed the John A. Blatnik Bridge in his honor on September 24, 1971.