"We were really able to break the mold and win a lot of Grand Slams and a lot of tournaments and not only that, but kind of change the face of tennis," Serena said Wednesday before an exhibition match against her sister in Lagos on Friday.
"We were able to break the mold in a sport that was really dominated by white people ... it doesn't matter what your background is and where you come from. If you have dreams, if you have goals, that's all that really matters."
The sisters, accompanied by their mother Oracene Price, are in Nigeria's largest city for the week.
The sisters swatted tennis balls with local children at a private club on Ikoyi Island, home to diplomats and many of the nation's wealthy.
If they have their way, the sisters will be hitting tennis balls for at least another four years, all the way to the 2016 Rio Olympics.
"It's our main goal," said the 31-year-old Serena, a three-time Olympic doubles gold medalist with Venus. "We were talking ... about how we can't wait to get to Rio. And obviously, bearing that we're both healthy, that's our goal to be there."
Venus, who is 32, agreed: "That's what we've begun preparing for."
Venus and Serena have teamed to win 13 Grand Slam doubles titles and won Olympic gold in doubles in 2000, 2008 and 2012. Serena also won the singles gold this year, while Venus won it in 2000.
Serena, who beat Victoria Azarenka 6-4, 6-4 to win the WTA Championships final in Istanbul last week, is ranked No. 3 in the world. Venus, diagnosed last year with an autoimmune disease that causes fatigue, has struggled with illnesses and injuries in recent months and is ranked No. 24.