São Paulo is a city built on immigrants: largely due to immigration, São Paulo's population grew a hundred-fold in 75 years to make it the country's second-largest city by 1950. Besides sheer numbers, the mass influx of people had a tremendous impact on the character of the city, breaking up the existing social stratification and removing economic and political power from the traditional elite groups at a much earlier stage than in other Brazilian cities.

Although there had been attempts at introducing Prussian share-croppers in the 1840s, mass immigration didn't begin until the late 1870s. Initially, conditions were appalling for the immigrants, many of whom succumbed to malaria or yellow fever while waiting in Santos to be transferred inland to the plantations. In response to criticisms, the government opened the Hospedaria dos Imigrantes in 1887, a hostel in the eastern suburb of Moóca. Now open to the public as the Memorial do Imigrante , Rua Visconde de Paraíba 1316, the hostel buildings house an immigration research centre and one of the best museums in São Paulo (Tues-Sun 10am-5pm; research facilities available only 1-4pm). The museum has a permanent collection of period furniture, documents and photographs, and regularly hosts temporary exhibits relating to particular aspects of immigration history. The main building itself is the most interesting feature of the complex, however, with vast dormitories and its own rail siding and platform for unloading immigrants and their baggage. Near the entrance, a separate building contained the rooms where new arrivals met their prospective employers, the government providing interpreters to help the immigrants make sense of work contracts. Designed to hold 4000 people, the hostel housed as many as 10,000 at times, the immigrants treated little better than cattle. In its early years, it was a virtual prison: the exit ticket was securing a contract of employment. Control was considered necessary since few immigrants actually wanted to work in the plantations, and there was a large labour leakage to the city of São Paulo itself. During most of the week the Memorial do Imigrante is little visited - perhaps due to its grim location, an unpleasant five- to ten-minute walk from Brás metrô station - but on Sundays and holidays, a beautiful nineteenth-century train connects the complex with Bresser metrô station (10am-5pm) and succeeds in drawing larger crowds.

Immigration to São Paulo is most closely associated with the Italians , who constituted 46 percent of all arrivals between 1887 and 1930. In general, soon after arrival in Brazil they would be transported to a plantation, but most slipped away within a year to seek employment in the city or to move on south to Argentina. The rapidly expanding factories in the districts of Brás, Moóca and Belém, east of the city centre, were desperately short of labour, and well into the twentieth century the population of these bairros was largely Italian. But it is Bixiga (or, officially, Bela Vista) where the Italian influence has been most enduring, as catalogued in the Museu Memória do Bixiga . Originally home to freed slaves, by the early twentieth century Bixiga had established itself as São Paulo's "Little Italy". As immigration from Italy began to slow in the late 1890s, arrivals from other countries increased. From 1901 to 1930 Spaniards (especially Galicians) made up 22 percent, and Portuguese 23 percent, of immigrants, but their language allowed them to assimilate extremely quickly. Only Tatuapé developed into a largely Portuguese bairro.

The first 830 Japanese immigrants arrived in 1908 in Santos, from where they were sent on to the coffee plantations. By the mid-1950s a quarter of a million Japanese had emigrated to Brazil, most of them settling in the state of São Paulo, and unlike most other nationalities the rate of return migration among them has always been small: many chose to remain in agriculture, often as market gardeners, at the end of their contract. The city's large Japanese community is centred on Liberdade , a bairro just south of the Praça da Sé and home to the excellent Museu da Imigração Japonesa .

São Paulo's Arab community is quite substantial. Commonly associated with petty commerce, Arabs started arriving in the early twentieth century from Syria and the Lebanon and, as they were then travelling on Turkish passports, they're still usually referred to as turcos. Family ties remain strong and, with the 1980s civil war in the Lebanon, the community was considerably enlarged. Many of the boutiques in the city's wealthy bairros are Arab-owned, but it's in the streets around Rua 25 de Março , north of Praça da Sé, that the community is concentrated.

The Jewish community has also prospered in São Paulo. Mainly of East European origin, many of the city's Jews started out as itinerant pedlars before concentrating in Bom Retiro , a bairro near Luz train station. As they became richer, they moved to the suburbs to the south of the city, but some of the businesses in the streets around Rua Correia de Melo are still Jewish-owned and there's a fine Eastern European restaurant ( Restaurante Cecília) and a synagogue in the area. As the Jews move out, Koreans have been moving in, with many prospering. The area is known as a centre of the rag trade and in the Korean-owned sweatshops the latest immigrant arrivals - Bolivians - are employed, often illegally and enduring appalling conditions.