A system comprising: one or more computers; and a computer-readable medium coupled to the one or more computers having instructions stored thereon which, when executed by the one or more computers, cause the one or more computers to perform operations comprising: receiving an audio signal that corresponds to an utterance recorded by a mobile device, determining a geographic location associated with the mobile device, adapting one or more acoustic models for the geographic location, wherein the adapting of the one or more acoustic models for the geographic location further comprises: incorporating data that references the geographic location into a feature space used by a single acoustic model, wherein the geographic location information is directly incorporated into the single acoustic model by directly stacking a two-dimensional, continuous latitude and longitude coordinate vector into the feature space, wherein the geographic location information is considered as part of the regular training process for a single acoustic model, and performing speech recognition on the audio signal using the one or more acoustic models model that are adapted for the geographic location. one or more computers; and a computer-readable medium coupled to the one or more computers having instructions stored thereon which, when executed by the one or more computers, cause the one or more computers to perform operations comprising: receiving an audio signal that corresponds to an utterance recorded by a mobile device, determining a geographic location associated with the mobile device, adapting one or more acoustic models for the geographic location, wherein the adapting of the one or more acoustic models for the geographic location further comprises: incorporating data that references the geographic location into a feature space used by a single acoustic model, wherein the geographic location information is directly incorporated into the single acoustic model by directly stacking a two-dimensional, continuous latitude and longitude coordinate vector into the feature space, wherein the geographic location information is considered as part of the regular training process for a single acoustic model, and performing speech recognition on the audio signal using the one or more acoustic models model that are adapted for the geographic location. receiving an audio signal that corresponds to an utterance recorded by a mobile device, determining a geographic location associated with the mobile device, adapting one or more acoustic models for the geographic location, wherein the adapting of the one or more acoustic models for the geographic location further comprises: incorporating data that references the geographic location into a feature space used by a single acoustic model, wherein the geographic location information is directly incorporated into the single acoustic model by directly stacking a two-dimensional, continuous latitude and longitude coordinate vector into the feature space, wherein the geographic location information is considered as part of the regular training process for a single acoustic model, and incorporating data that references the geographic location into a feature space used by a single acoustic model, wherein the geographic location information is directly incorporated into the single acoustic model by directly stacking a two-dimensional, continuous latitude and longitude coordinate vector into the feature space, wherein the geographic location information is considered as part of the regular training process for a single acoustic model, performing speech recognition on the audio signal using the one or more acoustic models model that are adapted for the geographic location.