EarthLink Municipal Networks today got the go-ahead from Philadelphia officials to build out the planned 135-mile Wi-Fi network in that city following approval of its 15-square-mile proof-of-concept trial network.

The company expects to have the entire city network completed by the third quarter, said Jerry Grasso, EarthLink’s director of corporate communications, making Philadelphia the largest metro Wi-Fi network in the country at that point.

“We are also building out Houston, which will be a 600-square-mile network but at the time Philadelphia is completed, it will be the largest,” Grasso said.

Philadelphia was the first major U.S. city to embark on building a Wi-Fi network and has pioneered the process in many ways. The city overcame opposition from local incumbents and legislative opposition to city-owned network. It created Wireless Philadelphia, a non-for-profit organization charged with making high-speed wireless Internet access available in the city.

The EarthLink Wi-Fi service will be available for free in some areas of the city, including the Historic District, Norris Square, Love Park and the Capitolo Playground in South Philly. Consumers who want to subscribe to the service can get it for $6.99 for the first six months and $19.99 after that for up to 1 Mb/s access. For 3 Mb/s, EarthLink will charge $9.95 for six months and $21.95 thereafter.

While the proof-of-concept success might be reassuring to other cities who are currently considering their own Wi-Fi networks--and most cities are--it doesn’t necessarily speed the pace at which the technology will be adopted, Grasso admitted.

“If there’s one thing we’ve learned from all of this, it is that every city is different, every city has its own processes that it has to get through,” he said.