The city of Santos in Brazil is the only area in the state of São Paulo where the form of address tu is found (Modesto 2006). The contact between Brazilians of European descent and Portuguese immigrants, in the beginning of the 20th century, is a possible cause of this phenomenon (Pereira & Frutuoso 2007). The literature on language contact highlights three important social variables which may lead to linguistic change. The first of these variables, as stated by Ravindranath (2015), is related to demography. The city of Santos became home to many Portuguese immigrants back in the first decade of the 20th century. The second variable is space and mobility (Britain 2013). Due to sanitary reforms (Mello 2007), the city of Santos had its urban mobility and spatial arrangement transformed, and this reshaped how the Brazilian and the Portuguese immigrants would move around the city. The last social variable is described by Dodsworth (2017) as the social role of individuals within a community. In Santos, the Portuguese immigrants had important roles in labor unions and helped to organize many of the harbor workers (Maram 1979). These factors converged to create a "solidary" scenario in Santos, which may have favored the use of more solidary forms of address where interlocutors could engage on more equal terms (see Brown & Gilman 1960) such as tu. In order to verify how the forms of address were used by Portuguese immigrants in the state of São Paulo in the beginning of the 20th century, 114 personal letters (Museu de Imigração de São Paulo 2019) were analyzed. Those immigrants who lived by the coast presented a higher use of tu in relationships among peers. In Santos, linguistic and social variables seem to have favored the use of tu and its usage persists today.