Despite their different social bases, Alfredão and Chiquinho maintained a close friendship, and in 1913 they decided to merge their teams to form União Futebol Clube.
[4] União’s first match was played against Flor da Índia, a small neighbourhood club based in the Brás district of São Paulo.
[3] In its formative years, União Futebol Clube remained an amateur team, composed mostly of wealthier players who viewed football as a leisure activity.
The notable exception was Alfredão, whose working-class background stood in contrast to that of his teammates but who played a pivotal role in the team’s establishment and early success.
[5] The first notable competition União Futebol Clube participated in was the Campeonato do Interior, organised by the Associação Paulista de Esportes Atléticos (APEA).
The outcome sparked outrage among União’s directors and supporters, culminating in the club sending an official letter to the APEA requesting its withdrawal from the organisation.
[3] During its amateur phase, União achieved its most significant triumph in 1947 by winning Group 1 of Zone 1 in the Campeonato do Interior, remaining undefeated with seven victories in ten matches played.
The poor performance, combined with increasing demands from the Federação Paulista de Futebol and mounting financial debts, led União to withdraw from the competition in 1952.
[11][3] During this period, União's squad notably included José Maria Marin, who would later serve as the president of the Brazilian Football Confederation (CBF).
[12] During União's absence from professional football, the club sought to meet the local population's demand for the sport by creating a veterans' team named XI da Saudade.
During this period, several renowned figures in Brazilian football, including Garrincha and Rivellino, represented XI da Saudade in special exhibition matches, further enhancing its reputation and appeal.
[14][15] Following the city’s strong performances in the Jogos Abertos do Interior in the late 1970s, former União player José 'Peru' Pierucetti decided it was time for Mogi das Cruzes to once again have a representative in the Campeonato Paulista.
[16][17] Neymar’s importance to the club was such that, after receiving an offer from Rio Branco in December 1989, ten União members pooled resources to pay NCz$ 100,000 for his playing rights, ensuring the winger remained part of the squad.
[3] Despite the improved performance in 1993, a reduction in the number of teams in the top two tiers of the Campeonato Paulista forced União to return to the Série A3 for the 1994 season.
[24] The poor performances continued during União Mogi's first three seasons in the fourth division, with the team suffering repeated eliminations in the first stage and managing only seven victories in 42 matches during this period.
One of the investors, Venílton Montini—a former União Mogi player from the 1990s—had previously achieved success in the lower tiers of São Paulo football, notably guiding Grêmio Barueri to a runner-up finish in the Série B2 in 2003.
In a single match played before a packed Nogueirão, the team from Mogi das Cruzes defeated Catanduvense 1–0, claiming the 2006 Série B1 title and etching its name into the club's history.
[32] The successful partnership with DARM Marketing Esportivo lasted only one year, ending in late 2006 due to disagreements with União Mogi's board of directors.
Brasil Sports' director, Márcio Borges, interfered heavily in football operations, including hand-picking the starting lineup during the competition.
Moreover, Brasil Sports failed to meet its financial commitments, as the company was mired in debt and had been operating irregularly since 1990, lacking even a proper office.
The 2011 season was marked by poor on-field performance, with the team suffering 10 defeats in 14 matches, and by serious allegations against head coach José Luiz Soares, who was accused of fraud, slander, defamation, and both moral and sexual harassment by players from the squad.
[40] In 1974, a public campaign named Luzes para o Futebol Mogiano ("Lights for Mogian Football") successfully raised funds from supporters and city residents, enabling the installation of floodlights at Rua Casarejos.
[40] However, financial struggles led União to sell the Estádio da Rua Casarejos in 1999 following an unsuccessful partnership with the construction company Marsil.
[41] In 1975, União Futebol Clube purchased a 128,200 m² plot of land in the Caputera neighbourhood for Cr$ 50,000, with the intention of building the Vila da Prata Training Centre on the site.