Coghlan died in his sleep Sept. 7 at his home in an assisted-living facility in Saugus, said his son, Pat.
"He was one of the busiest child actors of the late '20s and 1930s," said film critic and historian Leonard Maltin. "He was a fresh, freckle-faced boy with great All-American-type appeal."
Maltin, who interviewed Coghlan numerous times in his later years and often saw him at nostalgia gatherings, said, "He was just a sweet, sweet guy."
"When I met him," said Maltin, "he loved reminiscing, enjoyed meeting fans and was happy to be associated with what he knew was arguably the best serial ever made. His license plate said 'Shazam.' "
The 12-chapter “Adventures of Captain Marvel” serial from Republic Pictures marked the first time a comic book superhero was depicted on the big screen.
In Chapter 1, Batson is on an expedition to the Valley of the Tombs in Siam when a shaman gives him the ability to transform into Captain Marvel.
Coghlan was working on the 1941 MGM movie "Men of Boys Town" when his agent called to say Republic wanted to interview him for the role.
"I had no idea who Captain Marvel or Billy Batson were," Coghlan told Tom Weaver in an interview for Comics Scene magazine in 1994.
It was only after he was interviewed by the serial's producer and two directors that he stopped at a drugstore and bought a copy of the comic book.
"I said to myself, 'Hey, I do kind of look like that kid,' " he recalled.
Whenever Batson said "Shazam!" a giant flash and a cloud of white smoke appeared. And when the smoke cleared, Batson had become the mighty Captain Marvel (played by Tom Tyler).
"Every time we did that, they ignited flash powder, which was in a trough in front of me," recalled Coghlan. "And if the wind was unkind, I'd get the powder flash in my face and lose some eyebrows."
Coghlan was born March 15, 1916, in New Haven, Conn. After his parents moved to Los Angeles, he began working in films as an extra at age 3.
Billed as Junior Coghlan, he had small parts in films such as "The Spanish Dancer" (1923), starring Pola Negri; and played an uncredited "boy" in the Charles Chaplin-directed 1923 movie "A Woman of Paris: A Drama of Fate," starring Edna Purviance.
Director Cecil B. DeMille, who signed Coghlan to a five-year contract, called him "the perfect example of a homeless waif."
Among Coghlan's later silent-era credits were the DeMille-produced 1927 drama "The Yankee Clipper," starring William Boyd; and "Slide, Kelly, Slide," a 1927 baseball comedy starring William Haines. Coghlan went on to play James Cagney's Tom Powers character as a boy in "The Public Enemy" (1931), and he appeared with Harry Carey in "The Last of the Mohicans" (1932).
But as Coghlan grew older, many of the roles he had in the 1930s and '40s were uncredited, including playing a collapsing Confederate soldier in "Gone with the Wind" and playing small roles in films such as "The Courtship of Andy Hardy" and "Andy Hardy's Double Life."
A naval aviator during World War II, Coghlan continued his career in the Navy after the war and later served a number of years as the Navy's Hollywood-based liaison for motion pictures, television and radio.
After retiring as a lieutenant commander in 1965, he resumed his acting career, mainly in commercials, including serving as spokesman for Curtis Mathes televisions. He also worked in public relations for the Los Angeles Zoo and the Port of Los Angeles.
A former longtime resident of Los Alamitos, Coghlan wrote the 1992 autobiography "They Still Call Me Junior."
Coghlan's first wife, Betty, died in 1974; and his second wife, Letha, died in 2001.
In addition to his son, Coghlan is survived by three daughters, Libbey Gagnon, Cathy Farley and Judy Coghlan; three stepchildren, Gary, Ron and Ken Schwarzrock; and six grandchildren.