On 27 April 1917, the First Latgale Congress concluded in Rēzekne — dated 26–27 April according to the old style calendar, and 9–10 May according to the new style. On the second day, delegates adopted the historic decision to separate Latgale from Vitebsk Governorate and unite with Vidzeme and Kurzeme. The congress was not merely a regional meeting — it became one of the essential steps toward a united Latvian state.

During the First World War and the Russian February Revolution, Latgale still belonged administratively to Vitebsk Governorate rather than to the Baltic governorates. The congress’s decision created a political basis for the idea that Latgale, Vidzeme, and Kurzeme formed one Latvian-inhabited space — the future Latvia.