After working as a director for CBS network programs such as Person to Person and Face the Nation, he moved in 1956 to Channel 35, later WHYY-TV, Channel 12, and became the station's first black professional.
He produced several children's programs, including a 10-part series on the History of the Negro, which was narrated by actor Ossie Davis. The program was a collaboration of the efforts of several eminent black and white historians.
Yet, his best-known work while at WHYY may be the show he created and produced in 1968, Black Perspective on the News.
It was the first weekly series from WHYY-TV to air on the Public Broadcast System. It also was the first time on television that national issues were analyzed from the black perspective, while showcasing the talent of African American broadcasters.
Mr. Monagas was committed to seeing more African Americans in broadcasting and helped found the National Black Media Producers Association and an affiliate chapter in Philadelphia. He was appointed director of the national office in Washington.
"He visited every one of the PBS stations" to push minority hiring, said Howard Myrick, chair of the Temple University Department of Radio, Television and Film. "Those of us who came to work at PBS consequently, owe him a tremendous debt."
Mr. Monagas' dedication to his work at the producers association, and later as chief of the Equal Employment Opportunity Unit at the Federal Communications Commission in 1973, kept him on the road and away from the wife and daughter he loved dearly. He was married to the classical pianist Natalie Hinderas, who died in 1987.
"His daughter Michelle was his heart," said Clarence McKee, a co-owner of a CBS affiliate in Tampa who was Mr. Monagas' deputy at the FCC. "I remember when his wife and his daughter would come down (from Philadelphia) to visit him. He'd talk about them all day and say, 'My two ladies are coming.' It was a big sacrifice for him to be away from his family."
Mr. Monagas directed the drafting of FCC rules for minority ownership that made it possible for black men, such as McKee, to own broadcast stations. Mr. Monagas also helped put together the FCC equal employment opportunity guidelines that are still used today.
"He was a soft-spoken, unassuming man, but he worked diligently to distribute information to his community," said J. Clay Smith Jr., a Howard University law professor who was the FCC associate general counsel when Mr. Monagas worked there.
Though he was not a lawyer, Mr. Monagas joined the National Conference of Black Lawyers in Washington, rising on the strength of his broadcast knowledge to become treasurer of the group, said Mr. Smith.
He tried to share the few private moments he had with his family. Myrick said that associates and friends knew that they could usually find Mr. Monagas at his wife's many concerts in the Philadelphia area. He was very proud of her, and his daughter, friends said.
But his life was spent primarily helping people, particularly African Americans, get into broadcast media, said his daughter, Michelle Turner, an advertising account executive in Chicago.
"Having two parents with high-profile careers . . . there were always a lot of people in the house, lot of young people. I gained tremendous respect for them," she said.
Until 1990, Mr. Monagas was a lecturer in Temple's Radio-Television-Film Department. Myrick said he talked Mr. Monagas out of retirement.
"I called Lionel at his Willow Grove apartment, but he hesitated about accepting the position because he was preparing to do some traveling," said Myrick. "He said he'd call me back later. The next day, he showed up at my office, elegantly dressed, looking very professorial. He said, 'I'm ready.' And indeed, he was."
Mr. Monagas is survived by his daughter. Funeral services are private.