1. A computer-implemented method comprising: accessing, by a computer system, a search history that identifies one or more search queries that were previously submitted to one or more search services by a mobile computing device that is associated with a user; identifying, based at least in part on the search history of the mobile computing device, a geographic location to which future voice input from the user is likely to relate; selecting, by the computer system and based at least in part on the identified geographic location, a first grammar from among a plurality of grammars, includes a vocabulary that is relevant to the identified geographic location; and outputting, by the computer system, information that identifies the first grammar, wherein the outputted information causes a grammar used to analyze voice input from the mobile computing device to be changed to the first grammar.