She told the gathering of about 150 people, including dozens of children from the area, that playing tennis in an urban park "changed my whole life."
"I did not come from a tennis family. I didn't know what tennis was until I was 11 years old," she said.
She stressed that education and athletics are keys to a child's development.
"My parents always said, 'Keep a kid busy with education and sports, and they'll be too tired to get into trouble,' " King said, adding that her brother Randy Moffitt was a big-league pitcher.
"It's true. My brother became a major-league baseball player and I became No. 1 in the world, and it's because of my parents saying, 'Keep them busy, get them an education, and keep them in a sport.' "
The event was part of the third annual Love Your Park Week, a citywide celebration of service projects and activities at parks throughout the city.
The U.S. Tennis Association and the Freedoms helped fund the $550,000 renovation of Hunting Park's six tennis courts, which was completed in spring 2013. The Freedoms also handed out 100 tennis rackets to neighborhood children at Thursday's event.
On hand were girls from the tennis team of nearby Little Flower Catholic High School. The team started last year when the renovated courts were dedicated. Joining them were members of the boys' tennis team from Julia R. Masterman School.
The two groups volleyed together in a commemoration of King's famed 1973 "Battle of the Sexes" victory over Bobby Riggs.
Jefferly Toussaint, a senior on the Little Flower team, said she enjoyed playing at Hunting Park.
"I remember during freshman year, the courts were horrible. Now they have completely changed them," Toussaint said.
Justin Moody, 17, a junior at Masterman, said meeting King was "a once-in-a-lifetime experience. I've always dreamed of this moment. I always heard stories about Billie Jean King. So naturally, I just wanted to meet her."
Looking out at the children, King said, "From this we will have our future leaders. There will be kids who go on to college. There will be people who remember their experiences here and make a difference."