According to the history of the district Party Organisation, the uprising to seize power in the August Revolution 1945 in Quynh Nhai county took place later than in other localities in Son La, but it had a very important meaning. Its success smashed the harsh rule of the French colonialists, Japanese fascists and feudal minions, making the people the owners of the hamlets.

In Quynh Nhai, on the night of October 17, 1945, with the armed forces as the core, the revolutionaries were divided into two groups, one surrounded the house of the county ruler Deo Van Tum and the other broke into the military camp, forcing Tum to surrender, hand over weapons and disperse his troops. The uprising quickly won. On October 18, 1945, a large number of people in Quynh Nhai eagerly attended a meeting where the Provisional Revolutionary Committee of the country made debut.

Promoting the revolutionary spirit, Quynh Nhai together with the whole country gathered all resources for the protracted resistance wars against the French colonialists and American imperialists, liberating the South and reunifying the nation, as well as for the renewal process.

Quynh Nhai today has had great changes, step by step growing up from hardship. Especially, district successfully completed the construction of the Son La Hydropower Plant.

Promoting the strengths of the hydropower plant reservoir, Quynh Nhai is currently developing aquaculture with more than 4,000 fish cages, turning out nearly 2,000 tonnes per year. The whole district has nearly 2,000 hectares of fruit trees of all kinds with an annual output of 5,560 tonnes. It also maintains and develops more than 300 hectares of macadamia trees with the goal of forming a concentrated raw material area.

Quynh Nhai district boasts seven out of 11 communes recognized as a new-style rural area. It has effectively implemented the national target programmes and social security policies, contributing to rapidly slashing the poverty rate from 24.9% in 2015 to 5.82% in 2022. Defence has been strengthened while political security, social order and safety have been maintained stably.

Quynh Nhai is currently developing tourism services bearing the characteristics of the reservoir area with eight tourist sites. It has developed a spiritual tourist area with temples dedicated to Linh Son Thuy Tu (river and mountain gods and Quynh Nhai land founders) and heroin Han. Traditional folk dances, rituals and festivals have been preserved and promoted, creating a special highlight for the land, culture and people of Quynh Nhai, helping this land to become one of the attractive destinations for tourists inside and outside the province.

Quynh Nhai today is changing day by day. The Party Organisation, authorities and people of ethnic groups in the district have been continuing the revolutionary tradition and promoting the spirit of solidarity and joint work to realize the goal of making Quynh Nhai a new-style rural district by 2025.