The date the stamps will be issued has not yet been announced.
"Five individuals that have really had a great impact on the development of journalism over the years," Dave Failor, executive director of Stamp Services for the U.S. Postal Service, told CBSNews.com's Lloyd de Vries earlier this year. "It's the kind of stamp subject I enjoy seeing because it helps tell a story."
Sevareid was one of the pioneers who established CBS News, known as "Murrow's Boys," and was the first to report the French surrender to the Nazis in World War II. He also covered the Battle of Britain, the Burmese-China theater and Tito's partisans in Yugoslavia.
He headed the CBS News Washington Bureau for nearly a decade following the war, and was an early critic of Sen. Joseph McCarthy. He covered every presidential election from 1948 to 1976. From 1964 to his retirement in 1977, he was an analyst on The CBS Evening News.
"He had an excellence of fluency of style in his writing, and he deserved the high esteem in which he was held," former CBS News correspondent Richard C. Hottelet, another of "Murrow's Boys," said Friday.
Polk was killed covering the Greek Civil War in the late 1940s. He disappeared in May 1948, and his body was found a few days later. He had been shot at point-blank range with his hands and feet tied. He had been critical of both sides in the civil war.
"As I stand here today, it's still not clear to me whether he was murdered by the right-wing government of Greece or murdered by the communists," said Hottelet.
The George Polk Awards for electronic journalism are among the field's top honors.
"They're two very notable and honorable people," Hottelet said about Sevareid and Polk, both of whom he knew.
CBS is the only network whose news people have been honored on U.S. stamps. An Edward R. Murrow stamp was issued in 1994.
Gellhorn, considered one of the greatest war correspondents of the 20th century, covered conflicts from the Spanish Civil War (with Ernest Hemingway) to Vietnam, Israel's Six Day War and the U.S. invasion of Panama (when she was 81). She was also Hemingway's third wife, and died in 1998 at the age of 89.
John Hersey's best-known work was "Hiroshima," first an article about the atomic bombing for The New Yorker magazine, and then a book. He also wrote "A Bell For Adano," which won the Pulitzer Prize for fiction in 1945. During World War II, he covered the fighting in both Europe and Asia for Time, Life and The New Yorker. His 1954 article on the dullness of reading education inspired Dr. Seuss' "The Cat In The Hat."
Salazar "was a groundbreaker for Latinos in this country, but his work spoke to all Americans," Postmaster General John E. Potter told Los Angeles Times staffers last month. "By giving voice to those who didn't have one, Ruben Salazar worked to improve life for everybody. His reporting of the Latino experience in this country set a standard that's rarely met even today."
The Times had been among those campaigning for a Salazar stamp. Most of the requests to the Postal Service to honor journalists were on behalf of Salazar, led by the Los Angeles Times. There were also a number of requests for a Sevareid stamp, said Failor, and the Citizens' Stamp Advisory Committee decided to round out the issue with Gellhorn, Hersey and Polk.
Salazar was killed by a teargas projectile fired by a sheriff's deputy during an East Los Angeles riot he was covering in 1970. He was 42. In the 1960s, he covered the Dominican Republic, the Vietnam War and Mexico for the Times, before leaving in 1970 to become news director of Spanish-language television station KMEX.
"We're planning to issue the American Journalists stamps in the Spring at the National Press Club (in Washington), to coincide with activities to highlight the Press Club's 100th anniversary, USPS spokesman Mark Saunders told de Vries.
Other subjects on U.S. stamps next year include Bette Davis (in the Legends of Hollywood series), Disney Imagination, Minnesota statehood, Latin Jazz, the Year of the Rat, and Black Cinema.
By Lloyd A. de Vries
By Lloyd A. de Vries