The article presents the results of linguistic analysis of the documents from Fond «Mikhailovsky Stanitsa Ataman», State archive of Volgograd region (fund 332, register 1, 1734-1836). Sentence pattern analysis was aimed at discovering pragmatic value of the texts (mid 18th – beginning 19th cent.). The authors state that sentences as main constituents with complicated functionality build a 'vertical communication' structure. The imperative tonality might be used for issuing order or notification (with a shade of command). The comparison of the patterns representation in documents dated by the end of 18th and the beginning of the 19th cen. demonstrated unity in realization of the following genre parameters: addressee, function, dominant modality (tonality), information content, structure, space-and-time localization. The differences are explicated in the addresser position. In the sentences belonging to the end of the 18th cent. there is a solitary addresser, whereas in the 19th cent. it is conjoint, it points to a trend of formality in documentary communication. The transformations in the genre characteristics presented in the sentences under study are attested to some changes in the governmental structure of the Don Cossack Host, which is an extralinguistic reasoning, besides there are some intralingusitic reasons, in particular, evolution of official and documentary style of the Russian language.