Mr. Mitchell became the nation's youngest black legislator when he was elected to the Maryland House of Delegates at age 22. He served as a delegate from 1963 to 1967, when he was elected to the Maryland Senate, serving until 1986. He also contended in city elections during the civil rights era of the 1960s.
A year after leaving the Senate, Mr. Mitchell was convicted of trying to obstruct a grand jury, wire fraud and trying to tamper with a federal investigation. He served 18 months of a 41/2-year federal prison sentence.
He was named for his father, Clarence M. Mitchell Jr., the civil rights leader and longtime lobbyist for the National Association for the Advancement of Colored People. The courthouse on the west side of Calvert Street bears the elder Mitchell's name.
"I just loved Clarence Mitchell," said former state Sen. Julian L. Lapides, a colleague and friend who lives in Bolton Hill. "You might get angry at him, but you couldn't stay angry for long."
Mr. Lapides recalled that he and Mr. Mitchell entered the House of Delegates in the same year. "Our careers were parallel," Mr. Lapides said.
"When we first went into the Senate in 1967, there were no microphones. Clarence was one of the most eloquent speakers on the Senate floor and he was smart as he could be. If he were ever running late, he could be on his feet about an issue that affected him and give the most impassioned and eloquent response," said Mr. Lapides, praising him as "one of the best extemporaneous speakers" he ever knew.
Clarence Mitchell III's nephew, Del. Keiffer J. Mitchell Jr., a Baltimore Democrat, said one of his uncle's greatest accomplishments was helping establish equal rights in Maryland. He helped shape the state's public accommodations law in 1963 that required restaurants and hotels to serve all customers. When the law passed, it only applied to half of Maryland's counties.
"He led a rich life through public service," Keiffer Mitchell said. "To me, he was Uncle Clarence. He was a very gregarious, fun uncle. … He had a quick wit all the way up to his last moments."
Keiffer Mitchell said his uncle told him last week to celebrate his life, not mourn his death.
"He told me, 'I don't want any crying.' He said, 'I want you to have a party and celebrate my life,'" Keiffer Mitchell recalled. "He said he would be celebrating up in heaven."
Keiffer Mitchell said that when Mr. Mitchell was elected he could not join white legislators at dinner or stay in Annapolis hotels. Instead, he stayed at his grandparents' summer house at Arundel on the Bay.
From the floor of the State House in 1963, Mr. Mitchell said the public accommodations law was only a start.
"This by no means satisfies us," he said. "The rights of human beings should be given immediately, and not parceled out.
"If you segregate me because I am dirty, I can wash. If you segregate me because I have no education, I can get educated. If you segregate me, however, because of my color, I can do nothing about this. I cannot wash off my color."
Kweisi Mfume, who in 1986 beat Mr. Mitchell in the Democratic primary for the 7th Congressional district, said they shared a "mutual respect" nonetheless. Mr. Mfume went on to win the general election for the seat, which he held for five terms, succeeding Parren J. Mitchell, who was Mr. Mitchell's uncle but also Mr. Mfume's political mentor.
"Political development in West Baltimore would not have taken place at the pace it did without the influence and persona of Clarence Mitchell," said Mr. Mfume, the former head of the NAACP.
Mr. Mfume said his church, New Shiloh Baptist, was visited about a week ago by Mr. Mitchell's brother, Michael, who asked the congregation to pray for his sibling as his health deteriorated.
"I will miss his individuality, his resourcefulness, his distinctive character," Mr. Mfume said. "He was a political gladiator who overwhelmed his opponents and electrified his supporters."
Larry Young, the former state senator who now hosts a talk show on WOLB, said Mr. Mitchell ran a veritable West Baltimore political machine that did not just propel candidates into office but kept residents involved and informed about the issues.
"Clarence would hold monthly town hall meetings in the city. He made sure the people knew what was going on," said Mr. Young, who under Mr. Mitchell's mentorship was elected to the House of Delegates in 1974. "He would tell them, 'Annapolis is not going to come to you, you have to come to Annapolis.'"
Mr. Young, whose 23 years in the General Assembly ended when he was expelled from the Senate for ethics violations, credits Mr. Mitchell with "opening the door" for both his political and radio careers. Mr. Mitchell had hosted a Saturday show on WOLB and introduced him to its owner, Cathy Hughes. Until his illness took a turn for the worse, Mr. Mitchell was a frequent guest on and caller to Mr. Young's show.
"Clarence never forgot his constituency," Mr. Young said. "I would hope we would remember Clarence as a pioneer in the sense of his advocacy. … It was very important to him to speak for the underdog."
Former Mayor Sheila Dixon lauded Mr. Mitchell for his grassroots-level work as well.
"He was out there. On the streets. Out pounding the pavement," she said. "It is more than just lip service. He was an action-oriented individual."
Ms. Dixon recalled working with Mr. Mitchell on lead paint abatement, fighting blight in poor neighborhoods and boosting political representation for African-Americans.
Mayor Stephanie Rawlings-Blake said, "He was a legendary leader and community activist. It's a loss for the Mitchell family and for the city and the state."
The news of his death was first posted on the website for WBAL Radio, where Mr. Mitchell's son, Clarence M. Mitchell IV, known as C4, is a host. The radio station said his family was by his side when he died.
"My father instilled in us to want to improve the lives of someone else," Clarence Mitchell IV said in an interview with The Baltimore Sun. "He saw impossible odds and stood up against those odds."
His son recalled that his father had been to the White House to meet Presidents Harry S. Truman and John F. Kennedy.
"Kennedy told him and other young activists that if you want to see change, run for public office," he said.
While in the State House, Mr. Mitchell served as president of the National Black Caucus of State Legislators, deputy majority leader, majority whip and chairman of the executive nominations committee.
In addition to his service in the legislature, Mr. Mitchell worked as a mortgage banker, a real estate broker and a consultant.
Born in St. Paul, Minn., Mr. Mitchell later moved with his family to Northwest Baltimore, where they lived on Druid Hill Avenue. He was a graduate of Gonzaga College High School in Washington, where his father commuted to his Capitol Hill office.
In interviews in The Sun, he recalled first lady Eleanor Roosevelt was a dinner guest. "She had to come to our house," he recalled in 1985. "We couldn't take her to a fancy restaurant. They weren't open to us."
Mr. Mitchell attended the University of Maryland, Morgan State University and the University of Baltimore Law School.
As a young, articulate vote-getter, he joined two political battles in Baltimore.
In a September 1967 primary election, he battled against then-City Council member William Donald Schaefer for the presidency of the City Council. Mr. Schaefer defeated him 2 to 1. Mr. Mitchell ran on a ticket headed by attorney Peter G. Angelos, who later bought the Baltimore Orioles. Mr. Angelos was defeated by Mayor Thomas J. D'Alesandro III in that primary election.
In September 1971, Mr. Mitchell again sought a City Hall office. In the mayoral primary, he placed fourth, behind Schaefer, George Russell and Francis Valle. Mr. Mitchell polled a disappointing 6,582 votes to Mr. Schaefer's 94,809.
In November 1987, Mr. Mitchell was convicted of influence-peddling after being charged with accepting money to block a congressional investigation of the New York-based minority defense contractor Wedtech Corp. He served 18 months in federal prison.
He also was arrested in June 1996 on charges he assaulted his wife, Joyce. Mr. Mitchell denied the allegations. He said his legislative record showed his consistent advocacy for "the protection of women from spousal abuse." According to online court records, prosecutors dropped those charges.
Del. Nathaniel Oaks, a veteran Baltimore Democrat, is among the African-American elected officials who credited Mr. Mitchell with helping to launch their political careers.
"It was one of the shoulders that definitely I stood on to get to where I am today," said Mr. Oaks. "He was a mentor. He was an example for us to follow."
Mr. Oaks said Mr. Mitchell's legal troubles did little to affect his stature in his community, where he said the charges were widely viewed as an injustice.
"That's why we called him The Bear," Mr. Oaks said. "He came through the woods and he came through it with flying colors."
U.S. Rep. Elijah E. Cummings called Mr. Mitchell a mentor who inspired his own political career and "a giant — in the realm of public service, in the battle for civil rights, and in the hearts and minds of countless Americans."
"Clarence M. Mitchell III devoted his life to championing the underserved," Mr. Cummings said in a statement. "As the son of Clarence M. Mitchell Jr. and Juanita Jackson Mitchell, providing a voice to the voiceless was in his DNA."
Mr. Mitchell told The Sun in August 2008 that then-Sen. Barack Obama was "the beneficiary of those who laid the foundation for him to be where he is."
The former legislator described an encounter with Mr. Obama at a rally in Baltimore before he won the Democratic Party's presidential nomination.
Mr. Obama "turned to me, took both my hands and looked me right in the eye and said, 'Senator Mitchell, I want you to know I stand on your shoulders.' What he was saying to me was that he recognized that there were those that paved the way for him."
In addition to his son, survivors include his wife, the former Joyce Ellis; another son, Tariq Clarence Mitchell; five daughters, Lisa Mitchell Sennaar, Lauren Mitchell Williams, Shannon Mitchell, Sharon Mitchell and Angelique Spencer; and three brothers, Dr. Keiffer J. Mitchell Sr., Michael Bowen Mitchell Sr. and George Davis Mitchell, all of Baltimore. An earlier marriage to Clarice Byas Wheatley ended in divorce.
Service arrangements have not been finalized.
Baltimore Sun librarian Paul McCardell and reporters Jean Marbella, Erica L. Green, Scott Dance and Michael Dresser contributed to this article.