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CHICAGO — Chicago has 1,900 miles worth of alleys, more than anywhere else in the United States.

One in particular caught the attention of Don Posen in Lincoln Square, who wrote WGN to find out why some alleys have a groove down the middle of them. A quick email to the Department of Transportation and we had our answer: to help with drainage.

“There are several ways to mitigate drainage problems in alleys – many alleys were constructed with drainage at either side… some have a groove in the center and have the paving pitched toward the center to improve drainage,” a spokesperson said.

But Don’s question got us thinking: “What’s behind the design of Chicago’s alleys?”

Historian and geographer Dennis McClendon guesses he’s done more research than most on the history of alleys. After studying plats, which serve as blueprints for communities, he estimates that alleys date back to before America’s founding.

“As far as I can tell the first alleys come to be in the 1730s; the plans for Savannah, Georgia include these rear service lanes,” he said. “The alley becomes a very practical invention as cities are laid out in Ohio in the 1820s.”

Alleys were likely invented because of the popularity of horses in the west, McClendon said, invented out of necessity so hay could be brought in and manure taken out without tracking it through the front of a home.

This lithograph depicts Park Row in Chicago, circa 1866. (Courtesy: Chicago History Museum)

Roads in older American cities followed established travel lanes, or they were already too dense to add alleys. But Chicago was just getting started.

“It seems that by the time Chicago is laid out in the 1830s, they just expect a town in this part of the world to have alleys,” McClendon said.

These trends likely informed the original Thompson plat, a plan of early Chicago drawn up by surveyor James Thompson for the Illinois and Michigan Canal Commissioners, which included alleys on every block.

The Thompson plat served as a template for the building of Chicago (Courtesy: Chicago History Museum)

What makes Chicago unique, McClendon said, is since its founding city planners applied the same template over and over as they turned hundreds of miles of farm land into a city: eight blocks to a mile in one direction, 16 blocks to a mile in the other direction, and a 16-foot alley back in the back.

“That template of a 330′ by 660′ block turns out to be a really efficient way to subdivide farm land and turn it into the city that we know,” McClendon said.

This plat map of Chicago shows plans for the city circa 1836 (Courtesy: Chicago History Museum)

As dirt paths gave way to roads and alleys in the 1850s, wood became a popular paving material, according to Julius Jones of the Chicago History Museum. Blocks of wood harvested near the city were coated in coal tar, which had one major flaw: it’s highly flammable.

“So during the Great Chicago Fire, the streets literally caught on fire,” Jones said.

After the fire many streets and alleys were replaced, while others were just paved over. One of the few surviving wood alleys sits just a few blocks away from the history museum in the Gold Coast.

Even after the fire, alleys continued to be an integral part of Chicago. But they were passed over in other cities, and not just because they caught on fire.

“Beginning sometime in the late 19th century, new suburbs are being established that they want to give a more bucolic appearance, Riverside being the most famous one in the Chicago area,” McClendon said.

So some cities ditched alleys and the grid look for more winding roads. Newer cities like Los Angeles and Denver grew during the 20th century, when the automobile became more common, and people wanted driveways and side lanes to get to their homes instead of alleys in the rear.

Riverside follows a curved design instead of the alley-backed grid of Chicago (Image: Google)

Alleys may have fallen out of fashion for other reasons as well.

“Not only did a lot of trash get dumped, a lot of human waste got dumped as well,” Jones said. “It sort of became a place where the more sordid or dirtier aspects of the urban experience were done.”

But in more recent times, alleys have turned out to be a great asset to Chicago. They’re ideal for building utility poles, or even running fiber-optic cable for high-speed Internet.

And of course: Chicagoans still take their trash into the back, unlike cities like New York where it sits on the sidewalk.

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One thing is for sure: alleys are an integral part of Chicago’s identity. Many residents have fond memories of running through them as kids, or meeting neighbors as they worked on their car.

Newer plans even propose blocking off lesser-used alleys to turn them into outdoor cafés and other public spaces.

“There are actually organizations now thinking about ways to repurpose and reuse them in ways that bring communities together in the 21st century,” Jones said.

More reading on Chicago’s alleys

Tribune’s Barbara Mahany finds the most famous alleys, from smallest to most rat-infested

 Curious City’s extensive history gives even more details

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