The article initiates a publishing cycle devoted to the description of modernising processes taking place in the 19th century in the areas east of the Vistula River. The publications are intended to present the state, distribution and demographic structureof the rural population (peasants and the lower layers of the gentry) living within the parish of Trzcianne at the end of the first half of the 19th century; the parish was situated peripherally in relation to the changes taking place in Europe. A handwrittenlist of the inhabitants of the parish, dated 1843, is the main source. The features of the population under research were its extended reproduction and a tiny size of definite celibacy. The main goal of both basic social groups – peasants and pettygentry – was to found a family as soon as possible.