During her years on Council, Mrs. Clark chaired the Education Committee and, later, the Public Property and Public Works Committee. She was a longtime champion of the public schools and was known for her outspokenness during lively public debates.
In a statement released Sunday, U.S. Rep. Chaka Fattah (D., Pa.) said the city "lost a dedicated public servant."
"Gussie leaves behind a legacy of service and commitment to our community," Fattah said. "Everyone she touched knew of her passion for education, and she will be forever recognized for her tireless work improving the city's public schools."
Mrs. Clark died in the morning at Lankenau Medical Center. She is survived by her son, Mark; daughter Adrienne; and four grandchildren. Her husband, Leroy W. Clark, died in 2007.
Born 1932 in Uniontown, Ala., Mrs. Clark grew up in Fairmont, W. Va., and attended West Virginia State College. There she met her future husband, although they were not married until 1960, when they reunited in Philadelphia.
Mrs. Clark moved to Philadelphia for a job as an assistant at Color magazine, a publication aimed at African Americans and modeled after Life. When Color went out of business, Mrs. Clark enrolled in Drexel University, where she earned a master's degree in library science. After working as a librarian, she entered law school at age 39 and earned a degree from Temple University.
Several years later, she worked for U.S. Rep. William H. Gray III's congressional campaign. In 1979, heeding the encouragement of community members, she was elected to City Council.
Mrs. Clark was chairwoman of the Education Committee for 12 years, and for much of that time, she focused on getting more money dedicated to schools. She opposed vouchers and helped then-Council President John F. Street pass the 10 percent liquor tax, which earmarked revenue for the school district.
"Councilwoman Clark's advocacy for Philadelphia's public schools in particular won't soon be forgotten," Council President Darrell L. Clarke said in a statement Sunday.
He described Mrs. Clark as a peacemaker who found ways to bring people together. "When I first sought elected office, I encountered many Philadelphians who assumed I was Councilwoman Clark's son," Clarke said. "She was so popular back then with residents, I have to admit I was at times tempted to not correct them."
When she retired in 2000 at 67, Mrs. Clark told The Inquirer she simply felt it was time.
"I think elected office is like poker," she said then. "I think you have to know when to hold them and know when to fold them. And when you feel you have amassed a body of work that satisfies you."
Details on services were not immediately available.