1. A method of determining geographical relevance of a document, performed by one or more server devices, the method comprising: identifying, by one or more processors associated with the one or more server devices, a plurality of geographically relevant strings in the document; retrieving, by the one or more processors, a plurality of histograms respectively associated with the plurality of identified strings, each histogram relating occurrences of a particular identified string to geographic regions; combining, by the one or more processors, the plurality of histograms associated with the plurality of identified strings to obtain a combined histogram for the document; and associating, by the one or more processors, a particular geographic region with the document based on the combined histogram.