After the First World War ended in November 1918, there was jubilation and profound relief in Paris. However, unemployment surged, inflation soared, and rationing continued. Parisian households were limited to 300 grams of bread per day, and meat four days a week. A general strike paralyzed the city in July 1919. The Thiers wall, 19th-century fortifications surrounding the city, were demolished in the 1920s and replaced by tens of thousands of low-cost, seven-story public housing units, filled by low-income, blue-collar workers. Paris struggled to regain its old prosperity and peace.Combeau, Yvan, Histoire de Paris, pp. 85–86.

The French economy boomed from 1921 until the Great Depression reached Paris in 1931. This period, called Les années folles or the "crazy years", saw Paris reestablished as a capital of art, music, literature and cinema. The group of immigrant artists were referred to as the School of Paris. The artistic ferment and low prices attracted writers and artists from around the world, including Pablo Picasso, Salvador Dalí, Ernest Hemingway, James Joyce, and Josephine Baker. Paris hosted the 1924 Olympic Games, major international expositions in 1925 and 1937, and the Colonial Exposition of 1931, all of which left a mark on Paris architecture and culture.

The worldwide Great Depression hit Paris in 1931, bringing hardships and a more somber mood. The population declined slightly from its all-time peak of 2.9 million in 1921 to 2.8 million in 1936. The arrondissements in the city's center lost as much as 20% of their population, and the outer neighborhoods, or banlieues, grew by 10%. The low birth rate of Parisians was made up by a wave of new immigration from Russia, Poland, Germany, eastern and central Europe, Italy, Portugal and Spain. Political tensions grew in Paris, as seen in strikes, demonstrations and confrontations between the communists and Front populaire on the extreme left and the Action Française on the extreme right.Combeau, Yvan, Histoire de Paris, p. 91

Celebration and reconstruction after war

In 1919, Paris was a time of celebration and optimism. An enormous military parade was held on 14 July 1919 from Porte Maillot to the Place de la République, celebrating victory in the Great War. World leaders, including President Woodrow Wilson, arrived in Paris to join the celebrations and negotiate the terms of the new peace and a new map of Europe. Wilson was the first American president to visit Paris while in office, and he remained in Paris from December 1918, except a three-week visit back to the United States, until June 1919, when the Treaty of Versailles was finished.

The contents of the enormous warehouses at Vilgrain, where food rations for the army were stored, were sold at low prices to Parisians. In June 1919, bread rationing ended, and the food supply gradually returned to normal. In April, to create jobs for demobilised soldiers, the government decided to demolish the Thiers Wall, the ring of fortifications that had been built around the city from 1840 to 1844. There was discussion of turning the wide strip of land into a new park, but instead it was used for the construction of low-cost housing for Parisian workers. Demolition began on 5 May, and construction of seven-story public housing units began soon afterwards.

Another great ceremony was held 16 October 1919 to celebrate the consecration of the Basilica of Sacré-Coeur on Montmartre, completed just before the war. February 1919 saw the opening of the first commercial airline service in the world, between Paris and London. On 19 August 1920, the French National Assembly approved an allocation of 500,000 francs for the construction of the first mosque in Paris, to honor the sacrifice of tens of thousands of Muslim soldiers from the French colonies of Africa who had been killed in the war.

Parisians

The population of Paris had been 2,888,107 in 1911, before the war. It grew to 2,906,472 in 1921, its historic high. Many young Parisians were killed in the First World War, though a smaller proportion than from the rest of France, but this ended the steady population growth Paris had had before the war, and caused an imbalance in the population between men and women, which lowered both the marriage rate and the birth rate, and greatly increased the number of widows, orphans, and veterans handicapped by war injuries. The population of Paris was 2,871,429 in 1926; it rose to 2,891,020 in 1931, then dropped to 2,829,746 in 1936, and continued to drop slightly at each census until the 1960s, when the mass exodus of the Parisian middle class to the suburbs began.

Even before the First World War, Paris had had a higher proportion of foreign-born inhabitants than other European cities; in 1891, there were 67 foreign-born Parisians for every one thousand inhabitants, compared with twenty-four in Saint-Petersburg, twenty-two in London and Vienna, and eleven in Berlin. From 1919 to 1939, the number of Italian-born Parisians tripled in the Parisian region, although most settled in Île-de-France, outside the city limits. Two-thirds of the Italian-born Parisians were employed in construction and public works. Ten thousand Czechs and Slovaks moved into Paris in the same period. A large number of Armenians, survivors of the 1915 massacres, moved to the Paris region in the same period; poorer families moved to the suburbs, and wealthier families settled in the 9th arrondissement. Parisians born on the French islands of the Caribbean numbered about ten thousand and there were from one to two thousand Parisians from the French colonies in Africa. During the Spanish Civil War, several thousand refugees from the Spanish Republic moved to Paris, but many more settled in the southeast of France. Large numbers of Poles came to France in the same period, though most settled in the mining regions of the north and east. There was a significant migration of Russians to Paris after the 1917 Russian Revolution. Many former Russian aristocrats, who spoke French and were familiar with the city, found jobs as Paris taxi drivers.

Some of the immigrants to Paris in this period later returned to their native countries and had an important impact on world history. The future leader of Vietnam, Ho Chi Minh, worked as a pastry chef in Paris from 1919 to 1923, studying nationalism and socialism. Leopold Senghor arrived in 1928 to study and eventually became a university professor, a member of the Académie Française, and the first president of Senegal.

City government and politics

Since the time of Louis XIV, the French government considered Paris too important to be governed only by the Parisians. In 1919 the city had no elected mayor. The two most powerful figures, the prefect of the department and the prefect of police, were named by the national government. Paris did elect representatives to the National Assembly and to the municipal council. The greater part of the Parisian population were also moderates or conservatives, as the first elections after the war, in November and December 1919, showed. Two-thirds of the seats of the National Assembly from Paris were won by the Bloc National, which included conservative republicans, radicals and socialists who refused any alliance with the communists. In the elections for the municipal council, the Bloc National won forty-seven seats, against twenty socialists from the SFIO, three independent socialists, three radicals and seven conservatives. The new government took what measures they could to lessen the hardships of working-class Parisians. They opened crêches, day-care centers for the children of working women, and in 1923 and 1924 obtained a loan of 300 million francs to build public housing for low-income Parisians. From 1920 to 1949, 22,000 new low-income housing units were built for 129,000 persons.

In the 1924 elections for the National Assembly, Parisians expressed their discontent with high prices and new taxes by voting for a coalition of the left called the Cartel des gauches. The left won 356 seats, including 103 by socialists and 28 communists. However, in the municipal elections, where the rules were different, the Bloc National and conservatives won twenty-two seats, and the leftist front won fifteen, including seven communists. The communists came in first in nineteen quarters of the east Paris, in the 12th, 13th, 18th, 19th and 20th arrondissements, and established themselves as the most active and visible opposition party. In the 1928 elections, the communists took 11 of the votes in France, and 18.5 percent of the votes in Paris. The 1928 elections were won by the Union National, led by Raymond Poincaré, a coalition of the radicals and the right, which took thirty seats in the Paris council, against two-radical socialists, two socialists and five communists.

The municipal council had little power over major issues, which were decided by the national government, but it did have fierce debates over many symbolic issues, such as the names of Paris streets; in 1930 a council dominated by the left renamed a Paris street after Charles Delescluze, one of the leaders of the Paris Commune, and tried, unsuccessfully, to have all the streets named after saints given new names. From 1929 to 1936, many streets were renamed in honor of the Allies in the war; cours Albert I; avenue George-V, avenue Victor-Emmanuel-III, Avenue Pierre-I-de-Serbie, Avenue des Portugais, and Avenue de Tokyo (which was renamed Avenue de New-York in 1945). Other streets were renamed for France's victorious war leaders; Joffre, Foch, Pétain (also changed after World War II); Poincaré and Clemenceau.

Open and sometimes violent conflicts broke out between the socialists and communists. On 5 October 1929, a meeting of young socialists in a gymnasium was attacked by young communists, causing a hundred injuries. In the 1932 municipal elections, the left won a slight majority of the votes, but won only sixteen seats in the council, including one communist and three from the Party of Proletarian Unity, with a program almost identical with the communists, compared with twenty-eight from the right.

The rise of fascism in Italy and Germany, and the influence of Stalin and the Communist international, saw greater agitation in Paris on the extreme left and right. In January and February 1934, large and violent demonstrations against corruption in the parliament and government took place around the building of the National Assembly. On 6 February they turned into a riot; eleven persons were killed, and more than three hundred injured. The two extremes of the political spectrum confronted each other in Paris; the communists on the left, and new movements of the extreme right: the Croix de Feu, Jeunesse patriotes, Solidarité Française. The movements on the far left and far right each organized their own semi-military formations.

At the 14 July celebration in Paris 1935, the parties of the left marched together for the first time; this was the beginning of the Popular Front. In the elections of 26 April and 3 May 1936, the Popular Front, led by Leon Blum, won the national elections in France and the municipal elections in Paris. For the first time since 1919, the left won a majority of the votes in Paris and twenty-three of the thirty-nine seats on the municipal council. The communists were the big winners, taking 27.5 percent of the vote.