In the course of the administrative reform carried out in 1708 by Peter the Great, the area was included into Smolensk Governorate and remained there until 1929, with the exception of the brief periods between 1713 and 1726, when it belonged to Riga Governorate, and between 1775 and 1796, when Smolensk Governorate was transformed into Smolensk Viceroyalty. In 1776, Porechye was granted a town status, and Porechsky Uyezd with the center in Porechye was established. On 19 November 1918, Porechye was renamed Demidov, to commemorate the bolshevik Yakov Demidov, who was the chairman of the Uyezd Communist Party Committee and was killed during the Russian Civil War. Porechsky Uyezd was renamed Demidovsky Uyezd. In 1927, Demidovsky Uyezd was abolished.