There's a reason the name doesn't ring any bells: "Smithfield" is actually a contracted form of the street's original name, "Smith's Field Street." In a city as consonant-adverse as Pixburgh, that name was never going to last.
And as you may have guessed, "Smith's Field Steet" was so named because it touched on fields belonging to a guy named Smith who cared a lot about his fields. In fact, Devereaux Smith's name is associated with what might have been the most bitter property dispute of early American history. (Unless you count that whole settlers-versus-the-Indians thing -- but hardly anyone does.)
It may be hard to believe these days, when Red States and Blue States live in such harmony, but before the Revolutionary War, Pennsylvania and Virginia feuded bitterly over Pittsburgh. It's amazing anyone found time to fight the British.
In those days, the colony of Virginia coveted much of the land north of the Mason-Dixon Line. And the ambitious governor of Virginia found just the man to press the claim: a Pennsylvania-born schemer named Dr. John Connolly. In the words of one of his contemporaries, Connolly was "like a hungry wolf"; in exchange for personal power, he pledged to assert Virginia's control over western Pennsylvania.
Pennsylvania didn't recognize Virginia's claims, of course. So Pittsburghers were understandably bemused when, in 1774, Connolly started nailing up posters around town asserting that the governor of Virginia had put him in charge of the place.
The authorities of Westmoreland County (which included the entire region in those days) arrested Connolly for first-degree presumptuousness, but he was released after promising to return for his court date. And he did come back two months later -- with company. As historian Leland Baldwin wryly remarks in Pittsburgh: The Story of a City, 1750-1865, "Connolly ... kept his word like a man of the strictest honor when ... he suddenly rode into [town] followed by nearly two hundred buckskinned horsemen" sent from Virginia. With this muscle behind him, Connolly then took over the courthouse he was supposed to be tried in. They next day, his minions arrested three of the judges who were supposed to try him -- including Devereaux Smith, a prosperous Indian trader and respected local figure.
Smith was forcibly taken to Virginia, and though he was soon released, Connolly continued to persecute him. On June 10, 1774 Smith wrote a lengthy letter complaining of his family's desperation and "the tyrannical treatment they received from Dr. Connolly." While Smith had been imprisoned in Virginia, he wrote, Connolly sent "an armed guard of men to my house to take away a quantity of blankets and bags by force." When a friend, William Butler, tried to intervene, Connolly threatened to have Butler arrested too. For good measure, Connolly then "damned my wife, telling her ... that he would let her know that he commanded here, etc. etc. etc."
That was just the beginning of Smith's troubles -- and Pittsburgh's. Over the next several years, the Mon Valley history Elizabeth and Her Neighbors recounts, "Rival courts [were] trying to function in the same territory." Each colony chose its own officials to govern the area, and neither side recognized property lines or legal claims made by the other. As a result, throughout the 1770s there was "much ... acrimony and some exhibitions of brutality."
In fact, Smith himself was later accused of killing one of Connolly's minions, one George Ashton, in 1775. But it seems he never stood trial. The first shots of the Revolutionary War had been fired, and Connolly, who of course turned out to be a Tory loyal to England, had lost much of his influence. Even after the war was over, Pittsburghers apparently had little enthusiasm for prosecuting one of their own -- especially for killing an ally of the hated Connolly. According to History of Pittsburgh and Environs, "Smith lived unmolested in Pittsburgh for years after the Revolution."
The Virginia/Pennsylvania border dispute is little remembered today, but in some small way it anticipated the Civil War of a century later. Indeed, had the dispute of the 1770s turned out differently, Pittsburgh's industrial might could have ended up in Virginia's hands. Who knows how history might have changed? Smithfield Street would have a different name, at least. And, God forbid, we might have ended up with strange accents that made it hard to pronounce certain consonants.