Mr. Whitfield walks quickly up the brick sidewalk of West Pratt Street where it meets Martin Luther King Jr. Boulevard. With his shorts and colorful short-sleeve shirt, he looks like he could be a middle-aged man on vacation. But there’s a purposeful look in Mr. Whitfield’s eye as he scans the four lanes of idling cars backed up at the red light. He is about business. And as he walks, his shaved scalp shining with perspiration, he lets the people in the cars with their windows rolled up against the rain-forest humidity know exactly what he’s about in a booming voice.

“Cold, ya’ll, one dollar. Cold, how ’bout it? Cold, cold, one dollar. Cold. Ice cold.”

In his hands he grips the necks of three sweating bottles of Aquafina water. And before the light turns, he will have made another sale.

Behind him, under the shade of a low tree, three younger men have stopped to talk. At their feet, a few stray bottles of iced tea and Pepsi lie on the bricks next to a cooler. There’s another cooler maybe 10 yards away, sitting in the sun near the sidewalk on the MLK side of the intersection. That cooler belongs to Mr. Whitfield too.

“You can come catch us right here, or over there,” Ricardo Burrell, 26, says pointing toward MLK and raising his voice above the traffic noise. A white wifebeater hugs his wiry frame, and a patch of curly beard decorates his jutting chin. “We catch this way and that way so we don’t miss no sale.”

It’s just a couple of coolers and a handful of guys pacing the curb and darting out into stopped traffic to deliver a dripping bottle and retrieve a bill. It looks like any number of other ad hoc water-vending operations that pop up at busy intersections throughout Baltimore when the mercury crests the mid-80s. But this is no impromptu operation.

“We come out here like 9 or 10 and get off at like 6:30, 7 o’clock at night,” Mr. Whitfield’s 25-year-old son Greg Whitfield says, his voice a soft mumble, his hair worn in sandy braids.

“We work it like a job,” Burrell adds. “We’ve been doing it for about eight years, but his father’s been doing it for 15.”

Mr. Whitfield does not want to answer any questions from any reporters. He’s firm about it, but not rude; in fact, he comes off the brick steps where he’s been sitting in the shade to sell waters in the hot sun while his son, Burrell, and their friend Kwmaine Chase, 20, talk. Soon Mr. Whitfield’s 34-year-old son Jay Wallace shows up, a burlier version of his brother sporting a wispy goatee and three teardrops tattooed by his left eye, and joins the conversation.

People selling cold bottled water on Baltimore streets have become a familiar sight during the summer, so common as to escape notice much of the time. They each have different reasons for being out there, but from talking to a few of these seasonal peddlers, they catch a side of the city perhaps only witnessed from setting up shop on its corners.

To answer the most obvious question, they buy bottled water in bulk. “Wherever there’s a sale going on at,” Burrell says. “The mall, the dollar store, wherever we can get it the cheapest.” In addition to water, today they’ve also got bottled iced tea and some Pepsi products. A young man in designer jeans and a white shirt that’s impossibly crisp for such a sweltering day strolls by on Pratt and asks for a cold Dr. Pepper as if he expects there to be one. There is.

“Sometimes we’ve got Gatorade, diet. . . .” Chase adds.

On a hot day, like this scorching late-May afternoon, they say they can go through hundreds of bottles a day, and four or more cases of water alone. Everything’s a dollar.

“A case cost 12 dollars and we making 24 dollars,” Wallace says. “You double your money. I make 50 cents for each one I sell.”

MLK and Pratt isn’t some random corner, either. Wallace says they hold a mobile food-vendor license from the city to sell water from this particular corner. Not surprisingly, many people selling water to passersby don’t. Inquiries about such licenses are directed to Ryan O’Doherty, spokesperson for Mayor Stephanie Rawlings-Blake’s office, who says that as far as anyone on the board that oversees such licenses can recall, it has granted only two in the last two years.

“Dad made sure of [getting one],” Wallace says. “It cost $375 to be close to the Inner Harbor, and $25 for the application fee. You gotta renew that every year.”

Close to the harbor? Here, more than half a mile from the water, on the edge of West Baltimore?

“They consider this ‘close to the harbor,’” he says with the faintest hint of a grin. “They consider it [that way] ’cause of the traffic. If we was up there two blocks”—he points west, up Pratt—“it’d be 75 dollars.” (O’Doherty confirms that vendor licenses in the “downtown” area command a premium price.)

Standing where Wallace and the others are standing, you can look out through the heat shimmering over the intersection and spy a shirtless man in the median south of the intersection, digging through a cooler. A stroll out to the median later reveals him to be a young man but sunburned and bleary-eyed, standing in shorts and boots amid loose bottles, a backpack, and other random belongings. He declines to give his name or answer questions other than allowing that he’s there selling water. But as the afternoon wears on, cars stop beside his spot, moving on when the light turns, and are replaced by a new batch, over and over, all without him even turning around.

Mr. Whitfield and his workers, meanwhile, stalk the curb up and down the line of stopped cars, bottles in hand, making their pitch and making sales.

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