The Steel City was Mr. Mandela's third stop in a weeklong tour of the United States in 1991.
The African National Congress leader told local government, business and civic leaders how they could help his country -- several years still before he was elected president by a landslide in South Africa's first all-race election.
He urged his audience not to invest in South Africa until the white minority government was no longer in power.
The ex-boxer, lawyer and prisoner No. 46664 also delivered the H.J. Heinz Co. Foundation's Distinguished Lecture at Soldiers & Sailors Memorial Hall & Museum in Oakland.
He received a two-minute standing ovation as he entered the hall to speak for about 40 minutes to 2,000 invited guests.
"We want to ensure the emergence of a constitutional system in which there is no distinction among our people on grounds of color, race, gender or creed," Mr. Mandela said.
Brenda Berrian, a professor of Africana Studies at the University of Pittsburgh, attended the lecture, which was interrupted 15 times by applause.
She recalled that she approached Mr. Mandela to have a photo taken with him, to get his autograph and to talk with him about one of her colleagues, who had spent time imprisoned with Mr. Mandela.
Ms. Berrian said others there were touched by his demeanor.
"They were just excited. Here was the man who had spent 27 years in prison, and he was so gentle and calm, not filled with anger and hatred," she said.
While in Pittsburgh, Mr. Mandela had lunch at Heinz headquarters with top executives of local firms. For dinner, he met with a broader group of about 300 civic and business leaders at Pittsburgh Vista Hotel.
Heinz Chairman Anthony J.F. O'Reilly, who helped persuade Mr. Mandela to make Pittsburgh one of four stops on his second U.S. visit, said he was "absolutely" convinced that South Africa would be a safe investment after a change in governments.
Lexi Belculfine: email@example.com or 412-263-1878. Twitter: @LexiBelc. The Associated Press contributed.
First Published December 5, 2013 4:55 PM