Hanna was born in Winnsboro, the seat of Franklin Parish, to Andrew and Elizabeth Hanna. An Eagle Scout in his youth, Hanna became a lifelong advocate of the Boy Scouts and later received the group's Silver Beaver Award. In 1951, he graduated from Winnsboro High School, since Franklin Parish High School. He then entered Louisiana State University at Baton Rouge on a band scholarshi], having excelled at the trumpet, which he played in the LSU marching band. He sold advertising and served as the sports editor of the college newspaper, The Daily Reveille. He received his bachelor's degree in 1955.
Hanna launched his working career as a reporter at the Bastrop Daily Enterprise in Bastrop, the seat of Morehouse Parish north of Monroe. In 1956, hired by managing editor Bert Hatten, Hanna became the outdoors writer for the Monroe newspapers, now consolidated as the Monroe News Star then owned by the Ewing family and now a Gannett publication. He soon became the News-Star political editor, through which capacity he covered the Louisiana State Legislature and school desegregation.
Hanna was also a columnist, whose One Man’s Opinion appeared in numerous newspapers across the state. Hanna was on friendly terms with virtually all Louisiana governors beginning with Earl K. Long, whose last term extended from 1956-1960. He appeared in numerous documentaries, particularly on the Public Broadcasting Service, and was considered an expert on the Long family, a dominant Democratic faction throughout much of the 20th century in Louisiana. Among Hanna’s most acclaimed columns were among his last ones in 2005: (1) a study of Elliot D. Coleman, the sheriff of Tensas Parish from 1936–1960, and a state police bodyguard present at the assassination of Huey Pierce Long, Jr. and (2) another on the premature death from the after effects of a household fall of Louisiana Secretary of State W. Fox McKeithen, which tells of Hanna's friendship with McKeithen’s father, John J. McKeithen, governor from 1964–1972 and a native of nearby Columbia in Caldwell Parish in northeast Louisiana.
In 1965, at the age of thirty-two, Hanna purchased his first newspaper, The Concordia Sentinel. He also owned the Jonesville News-Booster in Jonesville in Catahoula Parish from 1967-1988. In 1974, he bought the Winnsboro paper. In 1996, he and his son, Sam Hanna, Jr. (born 1969), purchased The Ouachita Citizen. Hanna said that one of his more significant stories concerned the failure of the Delta Security Bank in Ferriday, which had ties to organized crime boss Carlos Marcello. Another Delta Bank still operates in Ferriday. Hanna was a director of the Concordia Bank & Trust Company in Vidalia, the largest independently owned bank in Louisiana, which has branches in Ferriday and other locations. He was twice president of the Ferriday Chamber of Commerce and a former president of Rotary International in Ferriday. He served on the founding board of directors of the private, Huntington High School in Ferriday.
Hanna died at St. Francis Hospital in Monroe at the age of seventy-two from emphysema. He and his wife, Mary Sue Hanna (born July 22, 1937) of Ferriday, also had two daughters, Mary Linda Rocconi (born 1961) and husband, August Todd Rocconi (born 1966), of Monroe and Lesley Hanna Capdepon (born 1963) and husband, Charles Keith Capdepon (born 1958), of Newellton, who is the parish engineer in Tensas Parish. He had three grandchildren and a daughter-in-law, the former Gena Crawford, the wife of son Sam Hanna, Jr. Though Hanna was a member of the First Presbyterian Church of Ferriday, his services were held in the larger sanctuary of the First Baptist Church of Ferriday. Interment was at Old Winnsboro Cemetery in Winnsboro.
Hanna was inducted in 1993 into the LSU Manship J-School Hall of Fame in Baton Rouge. On that occasion, he was asked to address the state legislature and receive accolades for his work. In 1995, Hanna became among the relatively few journalists inducted into the Louisiana Political Museum and Hall of Fame in Winnfield. In 2004, Hanna was entered into the "50-Year Club" by the Louisiana Press Association, which he joined as a student journalist. After Hanna's death, the press association renamed its annual "Best Regular Column" as the “Sam Hanna Award.
Upon his death, Kathy Spurlock, executive editor of The News-Star, called Hanna "the dean of the state’s newspaper publishers, the most knowledgeable about state politics, certainly the one with the most institutional knowledge."
Al Ater, a Ferriday farmer who was a former state representative and the acting Louisiana secretary of state at the time of Hanna's death and an honorary pallbearer at the funeral (along with former U.S. Representative John Cooksey of Monroe and former State Representative Bryant Hammett of Ferriday), said that few individuals had "their finger on the pulse of politics in Louisiana more than he did. He had a sixth sense of the happenings of the political situation in this state -- police jury to governor, your source for information was Sam Hanna."
One of Hanna’s columns, "A Christmas Quail Hunt", which reflects his love of quail hunting, was published annually in his papers. His son still runs the column each December in the three Hanna papers in his father's memory.