"Wahl began his work when he was contracted by real estate portal HomeGain to optimize the firm's search engine. At that time, real estate site maps were organized either by ZIP code or by census tract, which are both fairly arbitrary shapes drawn with disregard for the differences in the neighborhoods within. The Thomas Guides have long noted neighborhoods, but did not attempt to define where they begin and end.
Wahl saw that as a fatal flaw. "Neighborhoods are really important," he says. "For example, there's a census tract that combines downtown Berkeley and North Berkeley. In Berkeley hills, the average age is 57, and downtown it's 24. The incomes and values are completely different. It made me start thinking that we needed a different way to let people look for homes."
Working with 15 student interns, Wahl began phoning local-government planning departments, chambers of commerce and other community sources in hundreds of cities. "There's usually a librarian in each place who remembers the neighborhoods - the trick is finding them," Wahl says. "And you have to be careful about what people tell you, because they can tend to bleed their home into a better neighborhood."
Using the anecdotal data, Wahl drew polygons that contain the neighborhoods, then tacked them to base maps created by the U.S. Census. The new maps hit big. HomeGain went from limping into its last few million dollars of startup capital to being one of the leading real estate search sites."