The story of a map that helps you locate free flu shots in Philadelphia begins in Chicago.

"I've always been interested in public health," said Tom Kompare.

By day, Kompare is a Web developer at the University of Chicago. "At night I do some civic hacking," he said.

Kompare was at a meetup in September 2012 for local coders who build civic-minded Web apps on the side. He saw a presentation from Chicago's health department about flu shot accessibility and a corresponding data set.

"I looked at that and I said, 'Oh, I think I could build something with that and help 'em out,'" said Kompare.

A few days later, chicagoflushots.org was born — an easy-to-use map with both public health centers and private pharmacies where Chicagoans can get flu shots.

"Hey, we should talk to the city about if they want to use this on their website," Kompare recalled. And within a couple of weeks, there it was.

Traffic to the site during last year's fierce flu season was relatively strong. For this flu season, the site has seen about 6,600 views and 22,705 clicks on flu shot locations, according to Kompare.

"It was a fun little project for me personally," Kompare said, "just knowing that people will use it and it will make our city healthier."

That's a prevailing sentiment among civic-minded web geeks — test out some new skills, tinker with a new project and help folks while you're doing it: Open data and mapping as a one-two punch.

Kompare thought other cities might benefit, too.

"I built it in such a way with the idea in the back of my mind, 'Hey, if somebody else wants to use this, I want to make it very simple for them to reuse,'" he said.

Several other cities took note, seeing it as a useful tool for potentially improving public health.

"Here in Philadelphia someone said the same thing," said Philadelphia Chief Data Officer Mark Headd. "They said, 'Let's bring that to Philly.'"

Headd took the map made in Chicago and proposed a way to standardize the data behind it. The goal is scalability, helping other cities to adapt it even more easily.

"Did every address have a set of coordinates with it?" said Headd, by way of example. "Was there information about eligibility at every site, cost at every site?"

So far, San Francisco and Chicago have adopted the data standard proposed by Philadelphia.

Headd admits it's not the fanciest of projects — not a showstopper for civic coders, he says. But the goal is "better living through open data," fighting the flu by, hopefully, reaching Philadelphians who could use the help.

"The cost is zero," Headd said. "We're trying to get people that may not have a better option in terms of a pharmacy or something like that that requires insurance coverage or some sort of payment."

The Philadelphia map only has city-sanctioned flu shot locations, a few dozen public clinics and whatnot.

And honestly, the standalone version is a little clunky. There are other outfits who run sleeker sites plotting flu shot and other vaccine availability at your nearest pharmacy.

Philadelphia did recently put the flu shot location data into its citywide mapping platform — phila.gov/map, which is worth checking out.

But if you're a web savvy mapmaker who can play with open data, the city invites you: please, build away.

"That's the hope here," said Headd. "The hope is that people will see this data and use it and enhance it, with the ultimate goal of raising awareness in the city of Philadelphia of the availability of flu shots."