Wi-Fi marries Internet-based networking and radio broadcasting. Although still nascent, the technology is wildly popular. Geography is a central consideration in the functioning of Wi-Fi technology. Yet, its influence is just beginning to be investigated. Examination of the space of Wi-Fi poses problems as wireless data traffic is invisible to the eye and its underlying apparatus is impromptu and veiled to traditional geographic inquiry. A scheme for detecting Wi-Fi infrastructure and transmissions and analyzing their geographic properties is introduced in this article. The application of the scheme to the study of Wi-Fi geography in Salt Lake City, Utah, is described. A dense network of impromptu Wi-Fi infrastructure is found to permeate the city's built environment and the urban area has been blanketed in a fog of Wi-Fi transmissions without any centralized organization. This Wi-Fi cloud is surprisingly resilient to network and physical problems, although the early signs of geographically systematic throughput difficulties are evident in parts of the urban area. Wi-Fi appears to offer a solution to last-mile problems in the city and bucks the trend for polarization of the population on either side of a digital divide, at least for those with access to Wi-Fi-enabled hardware. Wi-Fi was found to strengthen existing urban geography. Activity is most prominent in the city's traditional commercial core. However, Wi-Fi also reaches out to interstitial and peripheral parts of the city. Although commercial penetration of Wi-Fi misses the traditional tourist and retail areas of the city, public Wi-Fi is being used to encapsulate and reinforce civic space in the city.