A location label may be determined for a portable electronic device. The location label may provide a textual indication of the particular location of a user of the portable electronic device, such as a restaurant name, or more generally a type of location of the user, such as simply a restaurant. The location label is determined based on a signature vector of operating environment characteristics of the portable electronic device. The operating environment characteristics may include sensor values, visible transmitters, radio connection information, executing applications or other operating environment characteristics that can have a value associated with them.