Well, that's an easy one: They don't. The part they call "the Flats" is, well, flat. And the part that's on the slope of the hill is called, well, "the Slopes." It's on the street signs and everything. You can also tell which you are in by how the natives refer to themselves and others. I've heard residents of the Flats refer to those on the Slopes as "slopies"; perhaps the slopies call flats residents "flatlanders." I wouldn't know -- whenever I go up there, the altitude just makes me dizzy.
Now that I've answered your question, a lesser columnist would at this point call it a day and hit the bars. But I'm a professional ... which means I hit the bars before I even started writing this article. And like that boozy guy on the next barstool who keeps rambling on about a subject you lost interest in 10 minutes ago, I'm just going to keep prattling on. (I'm actually not that guy, though; I'm the one three stools down who keeps to himself and mutters a lot.) So I'm gonna tell you a bit about the area's geography and history.
You've probably asked yourself: How did the Flats get so flat? (Or maybe that was me asking myself -- like I say, I tend to mutter a lot.) The answer's simple: The Flats lie on a flood plain, a broad expense created by the silt deposits of the mighty Monongahela River. And if you've ever wondered why it's taken so long to get the P.J. McArdle Roadway fixed, that's part of your answer: Supporting the roadway, which is suspended above the neighborhood between the Liberty Bridge and South 10th Street, means drilling through a lot of river sand until you find bedrock. Not an easy task.
In fact, as local scholar Charlie McCollester -- no stranger to the barstool himself -- was the first to tell me, you can't really say that the Slopes are on a "hill" at all. Geologically speaking, hills are formed up an upward thrust in the earth's crust, and that didn't happen in Pittsburgh. All that we have here are plateaus that have been worn away by rivers, leaving a few high points behind. Our "hills," then, are just the places where valleys aren't. (Did that make sense? If not, ignore me; I'll just go on muttering to myself.)
Much of the South Side, Slopes and Flats both, was granted to one John Ormsby in 1770, a reward for his service as a major in the French and Indian War. Originally, the Flats were used as farmland, but Ormsby's son-in-law, Nathaniel Bedford, laid out a town along the Flats that he called Birmingham -- a tribute to his hometown in England and, coincidentally, a portent of the area's industrial future. Principal streets in the Flats are named after his wife and her sisters -- Sidney, Sarah and Mary. Carson Street was named for a friend of his. Mount Oliver, a community tucked in behind the Slopes, was named after another member of the Ormsby clan: John's son Oliver.
The line separating Slopes from Flats -- like so many dividing lines in Pittsburgh -- is very clear: It's the Norfolk Southern railroad and/or Josephine Street. South of Josephine, it's all uphill. And architectural historian Franklin Toker contends that in Pittsburgh's formative years, this border also marked "an ethnic division with Germans on the slops and Eastern Europeans on the flats."
Their history diverged sharply as well: The Flats' proximity to the river and its level terrain made it an ideal location for heavy industry, and in the 19th century it was home to the largest glass-making facilities in the country. It also boasted the sprawling Jones & Laughlin steel complex, but we don't like to talk about that stuff anymore. The Slopes, by contrast, couldn't support much heavy industry unless you hung it from a trapeze. But the hillside contained deposits of coal, and it made convenient housing for those who worked in the Flats. A series of inclines were built to carry both carbon-based assets -- labor and fuel -- down the hillside to the flats.
Today, of course, you don't see much heavy industry anywhere in Pittsburgh, but the two neighborhoods still retain distinct differences. Homes on the Slopes, as Toker notes, tend to be wood-frame structures perched on twisty streets, while the Flats are lined with brick homes arranged in an orderly grid. But both, I'm happy to say, have plenty of bars.
Which reminds me ...