The new exhibit on slavery in Pittsburgh during the 18th and 19th century at the Sen. John Heinz History Center is an enriching "must" visit for every Pittsburgher, of whatever hue.

The subject of race in the United States -- whatever happened last night and whatever it may mean for this country -- remains a subject of great passion for Americans. Race was the leitmotif of Sen. Barack Obama's campaign for the presidency, even though he himself was not a descendant of slaves. Slavery still lies near the heart of the matter in the history of the United States.

It is first of all a shock to think that there was slavery in Pittsburgh until about 1850. The last legal paper that refers to a slave is dated 1857. Older people's great-grandparents were adults at that time, and it is possible that grandparents could have passed along stories from them to some of us as children.

The Heinz exhibit presents a trove of visual and other documentation. The key Pennsylvania law was the Act for the Gradual Abolition of Slavery, passed in 1780. Notice the "gradual." A lot of loopholes in the law, reflecting different Pennsylvanian views of the subject by moralists, business people and others, needed to be closed before the slave population of the commonwealth, 6,000 in 1780, could be said to have been reduced to zero as of 1850.

There are messages in the exhibit for white and black Pittsburghers. I was breezing cheerfully through a 1780-82 list of slaveholders, spotting prominent Pittsburgh names -- Craig, Neville, McKee and O'Hara.

Then I got to "Gaotjer Simpson." My first thought was, "No way." We Simpsons were Northerners. Some were from Pittsburgh, but we were definitely not "old Pittsburghers." We weren't rich. And so forth. Then I reflected a little more, thinking of the broad, sometimes dodgy, largely unknown-to-me character of some of my family and concluded, "How do you know, smart guy?"

That is one of the points of this exhibit. Unless one is definitively not from here, it prompts more research.

There is more. In 1800 a Pittsburgh census listed 64 slaves out of a population of 2,400. It doesn't sound like much, but that was 20 years after the act gradually abolishing slavery in Pennsylvania. But there was still indentured servitude, for whites as well as for blacks. And freed slaves or free blacks were well advised to possess and even carry a "Certificate of Freedom" since slavecatchers from the South were to be found in Pittsburgh.

The Pittsburgh Gazette, the predecessor of the Post-Gazette, carried runaway slave ads until 1837, 57 years after slavery in Pennsylvania was supposed to have been gradually abolished.

The more I wandered around the exhibit, read and thought about it, the more I realized that it was not at all a "Black History" event. It was American history, a point made to me forcefully by Dr. Robert Hill, vice chancellor of the University of Pittsburgh, who, with Pitt Chancellor Mark A. Nordenberg, was the driving force behind the exhibit.

What must Pittsburgh have been like with slaves and, later, with black indentured servants as an important part of life? What advantage did factory owners who were slaveholders have over competitors who were not? What if it was a question of domestic slaves at home, doing unpaid work, as opposed to paid household help?

Then there was the sexual angle. How did some Americans that are considered to be black get so light? It wasn't reverse suntan, for sure. The exhibit makes it clear that one element in slavery was concubinage. The word "pedophilia" does not appear, although there is clear mention in the exhibit of the youth of some of the girls involved.

Brazilians, who didn't get around to abolishing slavery until 1888, have a saying that "money whitens." The exhibit deals quite frankly with that subject, talking about the different gradations of "black" or "white."

I didn't really focus on America's perception of color until I had lived for two years in Africa and came back. In Africa many people are really black. Most African Americans aren't. Yet Americans are considered to be either black -- even if just a little black -- or white, although, again, the exhibit goes into sensitive gray-area ascriptions such as "high yellow," which does not refer to Asians. I'll bet that readers only of a certain age know what "to pass" (as white) means. That phenomenon is also an element in the exhibit.

Slavery appears to have been hard for Pennsylvanians to wrestle with. Many were Quakers, yet they were businesspeople and farmers, partly attracted by the idea of free labor. It was a regional issue. It wasn't clear until 1779 that this part of Pennsylvania was not to be part of Virginia, a slave state. West Virginia, a step across the border, was part of Virginia until 1863, many years after slavery was abolished in Pennsylvania.

Another piece of introductory history that one can carry away from the slavery exhibit is a knowledge of African-American Pittsburghers who led the fight for abolition. These were people I had never heard of -- Henry Highland Garnet, William Hunter Dammond, Martin R. Delany. There's nothing about them in the Founders' Room at the Duquesne Club. They also must have descendants, perhaps here, just as do the Mellons, Carnegies and Fricks.

I give full tribute to the Heinz History Center and to the University of Pittsburgh for putting the information out there. It is up to all of us with curiosity about our past and a desire to understand the present of Pittsburgh to go look at it. After that, the pursuit of the rest of the story is up to the viewer. Do I want to know if Gaotjer Simpson was a relative or not? If he was, then what?