The soviet was established in March 1917 after the February Revolution as a representative body of the city's workers and soldiers, while the city already had its well established city council, the Saint Petersburg City Duma (Central Duma). During the revolutionary days, the council tried to extend its jurisdiction nationwide as a rival power center to the Provisional Government, creating what in Soviet historiography is known as the Dvoyevlastiye (Dual power). Its committees were key components during the Russian Revolution and some of them led the armed revolt of the October Revolution.
Before 1914, Petrograd was known as Saint Petersburg, and in 1905 the workers' soviet called the St Petersburg Soviet was created. But the main precursor to the 1917 Petrograd Soviet was the Central Workers' Group (Центральная Рабочая Группа, Tsentral'naya Rabochaya Gruppa), founded in November 1915 by the Mensheviks to mediate between workers and the new Central Military-Industrial Committee in Petrograd. The group became increasingly radical as World War I progressed and the economic situation worsened, encouraging street demonstrations and issuing revolutionary proclamations.
On January 27, 1917 (all dates Old Style) the entire leadership of the Central Workers' Group was arrested and taken to the Peter and Paul Fortress on the orders of Alexander Protopopov, the Minister of the Interior in Imperial Russia. They were freed by a crowd of disaffected soldiers on the morning of February 27, the beginning of the February Revolution, and the chairman convened a meeting to organize and elect a Soviet of Workers' Deputies that day.
That evening, between 50 and 300 people attended the meeting at the Tauride Palace. A provisional executive committee (Ispolkom) was chosen, named “Provisional Executive Committee of the Soviet of Workers’ Deputies” and chaired by Nikolay Chkheidze, and with mostly Menshevik deputies. (Chkheize was replaced by Irakli Tsereteli in late March). Izvestia was chosen as the official newspaper of the group. The following day, February 28, was the plenary session; elected representatives from factories and the military joined the soviet, and again moderates dominated. Non-representative voting and enthusiasm gave the Soviet almost 3,000 deputies in two weeks, of which the majority were soldiers. The meetings were chaotic, confused and unruly, little more than a stage for speechmakers. The party-based Ispolkom quickly took charge of actual decision-making.
The Executive Committee members came only from political groups, with every socialist party given three seats (agreed March 18). This created an intellectual and radical head to the peasant-, worker-, and soldier-dominated body. The Executive Committee meetings were more intense and almost as disorderly as the public meetings, and were often extremely long.