In the period from 1922 to 1941, Engels was the administrative center of the Autonomous Soviet Socialist Republic of the Germans of the Volga region. The pre-war decade was a time of rapid industrial growth. In the late 1930s, one of the country's largest meat-packing plants was built. On the basis of the railway workshops, the Pokrovskaya Mechanical Plant was established, which mastered the production of snowplows and snow-removing trains. In 1934, the first machine-building plant was produced. In these years, a glutinous plant, a bakery, a printing plant were built. Before the Great Patriotic War in Engels, there were 73,300 inhabitants, of whom 6,000 worked in urban industrial enterprises.
The city of Engels became the third after the Saratov and Marx Volga region. Marx and the last capital of the ASSR of the Volga Germans.